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Toxicity Effects

CAS Registry Number: 79-43-6

Selected toxicity information from HSDB, one of the National Library of Medicine's databases. 2.

Names 1

  • 2,2-Dichloroacetic Acid
  • Bichloracetic Acid
  • Bichloroacetic Acid
  • DCA
  • Dichloracetic Acid
  • Dichloroacetic Acid (Water Disinfection Byproducts)
  • Dichloroacetic Acid (Water Disinfection Mode)
  • Dichloroacetic acid
  • Dichloroethanoic acid
  • Water disinfection byproducts (Dichloroacetic acid)
  • Water disinfection model (Dichloroacetic acid)

Human Toxicity Excerpts

  • ALTERNATIVE and IN VITRO TESTS: In this study hPPAR(alpha) levels in six human liver tissues and in a long-term human hepatocyte cell line are compared. PPAR(alpha) levels varied significantly between individual tissues and are generally lower than PPAR(alpha) levels detected in mouse liver. Long-term cultured human hepatocytes display PPAR(alpha) levels only slightly lower than cultured mouse hepatocytes. Transfection studies examining the endogenous hPPAR(alpha) activity revealed little or no receptor activation, even following treatment with high concentrations of peroxisome proliferators. In contrast human hepatocytes transfected with mPPAR(alpha) and mRXR(alpha) display increased expression of PPAR(alpha), and increased PPRE-reporter activity when treated with WY-14,643, trichloroacetate, and dichloroacetate. /Dichloroacetate/[Walgren JE et al; Res Commun Mol Pathol Pharmacol 108 (1-2): 116-32 (2000)] **PEER REVIEWED** PubMed Abstract
  • ALTERNATIVE and IN VITRO TESTS: The ... studies were aimed at using both primary and long-term human hepatocyte cultures to study the effects of trichloroacetate (TCA), dichloroacetate (DCA), and a potent peroxisome proliferator, WY-14,643, on peroxisomal activity and DNA synthesis in human hepatocytes. Peroxisome proliferation, as assessed by palmitoyl-CoA oxidation activity, was below the limit of detection in all human cell lines tested. However, the human cell lines did display small but significant increases in CYP450 4A11 1 levels following treatment with WY-14,643 (0.1 mmol/L), indicating that the CYP 4A11 gene may be regulated by peroxisome proliferator-activated receptor alpha in humans. Similarly to their effect in rodent hepatocyte cultures, TCA and DCA were not complete mitogens in human hepatocyte cultures. In fact, DNA synthesis tended to be significantly decreased following treatment of the cells with WY-14,643, TCA, or DCA. In contrast to rodent hepatocyte responses, TCA and DCA did not increase palmitoyl-CoA oxidation and caused a decrease in DNA synthesis in human hepatocyte cultures, suggesting that humans may not be susceptible to TCA- and DCA-induced hepatocarcinogenesis. /Dichloroacetate/[Walgren JE et al; Cell Biol Toxicol 16 (4): 257-73 (2000)] **PEER REVIEWED** PubMed Abstract
  • BIOMONITORING: A study was conducted to determine if dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) urinary excretion rates are valid biomarkers of chronic ingestion exposure to these disinfection by-products of chlorination of drinking water. Entire first morning urine voids, time-of-visit urine samples, and tap water samples were collected from 47 female subjects. In addition, a 48-hr recall questionnaire was administered to determine the amounts and types of liquids ingested by each subject as well as other exposures that could lead to DCAA and TCAA urinary excretion. The TCAA excretion rate for the first morning urine samples was significantly correlated with the estimated 48-hr TCAA ingestion exposure for 25 subjects whose ingestion exposures primarily occurred at home, while the DCAA excretion rate was not correlated with the DCAA ingestion exposure. Thus, urinary TCAA appears to be a valid biomarker of chronic ingestion exposure to TCAA from chlorinated water, while urinary DCAA is not. It is proposed that the difference in the biological half-lives between these two compounds is the rationale for this finding. The biological half-life of TCAA is longer than successive exposure intervals; thus TCAA accumulates until it reaches a steady state. The half-life of DCAA is shorter than successive exposure intervals; thus DCAA is almost completely metabolized following an exposure and is eliminated from the body. This study suggests that biological half-life, exposure interval, and sample collection interval should be considered in selecting biomarkers and designing studies to validate them.[Kim H et al; Environ Res 80 (2 Pt 1): 187-95 (1999)] **PEER REVIEWED** PubMed Abstract
  • SIGNS AND SYMPTOMS: The neurotoxic effects of dichloroacetic acid observed repeatedly in experimental animals have rarely been documented in clinical trails. Drowsiness is a fairly frequent side effect of dichloroacetic acid and has been observed in healthy volunteers, adults with type I diabetes and patients with lactic acidosis. A patient with homozygous familial hypercholesterolemia who received single doses of 50 mg/kg body weigh dichloroacetic acid daily for four months developed reversible peripheral neuropathy characterized by loss of reflexes and muscle weakness; the effect subsided several weeks after cessation of administration of dichloroacetic acid.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 280 (1995)] **PEER REVIEWED**

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Non-Human Toxicity Excerpts

  • ALTERNATIVE and IN VITRO TESTS: ... To distinguish whether the in vivo glycogenic effect of dichloroacetate (DCA) was dependent on insulin and insulin signaling proteins, experiments were conducted in isolated hepatocytes where insulin concentrations could be controlled. In hepatocytes isolated from male B6C3F1 mice, DCA increased glycogen levels in a dose-related manner, independently of insulin. The accumulation of hepatocellular glycogen induced by DCA was not the result of decreased glycogenolysis, since DCA had no effect on the rate of glucagon-stimulated glycogen breakdown. Glycogen accumulation caused by DCA treatment was not hindered by inhibitors of extracellular-regulated protein kinase kinase (Erk1/2 kinase or MEK) or p70 kDa S6 protein kinase (p70(S6K)), but was completely blocked by the phosphatidylinositol 3-kinase (PI3K) inhibitors, LY294002 and wortmannin. Similarly, insulin-stimulated glycogen deposition was not influenced by the Erk1/2 kinase inhibitor, PD098509, or the p70(S6K) inhibitor, rapamycin. Unlike DCA-stimulated glycogen deposition, PI3K-inhibition only partially blocked the glycogenic effect of insulin. DCA did not cause phosphorylation of the downstream PI3K target protein, protein kinase B (PKB/Akt). The phosphorylation of PKB/Akt did not correlate to insulin-stimulated glycogenesis either. Similar to insulin, DCA in the medium decreased IR expression in isolated hepatocytes. The results indicate DCA increases hepatocellular glycogen accumulation through a PI3K-dependent mechanism that does not involve PKB/Akt and is, at least in part, different from the classical insulin-stimulated glycogenesis pathway. Somewhat surprisingly, insulin-stimulated glycogenesis also appears not to involve PKB/Akt in isolated murine hepatocytes. /Dichloroacetate/[Lingohr MK et al; Toxicol Sci 68 (2): 508-15 (2002)] **PEER REVIEWED** PubMed Abstract
  • ALTERNATIVE and IN VITRO TESTS: Dichloroacetate (DCA) and trichloroacetate (TCA) ... have been previously shown to induce superoxide anion (SA) production and cellular death when added to J774.A1 macrophage cultures. In this study, the effects of superoxide dismutase (SOD) and polyclonal tumor necrosis factor-alpha (TNF-alpha) antibodies on DCA- and TCA-induced SA production and cellular death have been tested on the J774.A1 macrophage cultures. TCA and DCA were added to different cultures either alone, each at a concentration of 16 mM, or in combination with SOD (2-12 units/mL), or with TNF-alpha antibodies (10 and 25 units/mL). Cells were incubated for 48 hr, after which cellular death/viability, lactate dehydrognase (LDH) leakage by the cells, and SA production by the cells were determined. While TCA and DCA caused significant cellular toxicity, indicated by reduction in cellular viability and increases in LDH leakage and SA production, SOD addition resulted in significant reduction of the effects induced by the compounds. On the other hand, addition of TNF-alpha antibodies to the DCA- and TCA-treated cultures resulted in significant reduction of DCA- but not TCA-induced cellular death and SA production by the cells. Although these results suggest a significant role for SA in DCA- and TCA-induced cellular death, they may also suggest two different mechanisms for the chloroacetate-induced SA production by the cells.[Hassoun EA, Kini V ;Comp Biochem Physiol C Toxicol Pharmacol. 2004 Jun;138(2):113-20.] **PEER REVIEWED** PubMed Abstract
  • ALTERNATIVE and IN VITRO TESTS: Rat hepatocytes, cultured in growth factor-free medium, were treated with 0.01-1.0 mM dichloroacetate (DCA) ... for 10-40 hr; cell replication was then assessed by measuring incorporation of 3H-thymidine into DNA and by cell counts. DCA ... did not alter 3H-thymidine incorporation in the cultured hepatocytes. Although an increase in cell number was not observed, DCA treatment significantly abrogated the normal background cell loss, suggesting an ability to inhibit apoptotic cell death in primary hepatocyte cultures. Furthermore, treatment with DCA synergistically enhanced the mitogenic response to epidermal growth factor. The data indicate that DCA ... /is not a direct mitogen/ in hepatocyte cultures... /Dichloroacetate/[Walgren JL et al; Toxicology 211 (3): 220-30 (2005)] **PEER REVIEWED** PubMed Abstract
  • ALTERNATIVE and IN VITRO TESTS: The mechanism of dichloroacetate (DCA neurotoxicity) /was investigated/ using cultured rat Schwann cells (SCs) and dorsal root ganglia (DRG) neurons. Myelinating SC-DRG neuron co-cultures, isolated SCs and DRG neurons were exposed to 1-20 mM DCA for up to 12 days. In myelinating co-cultures, DCA caused a dose- and exposure-dependent decrease of myelination, as determined by immunolabeling and immunoblotting for myelin basic protein (MBP), protein zero (P0), myelin-associated glycoprotein (MAG) and peripheral myelin protein 22 (PMP22). Partial recovery of myelination occurred following a 10-day washout of DCA. DCA did not affect the steady-state levels of intermediate filament proteins, but promoted the formation of anti-neurofilament antibody reactive whirls. In isolated SC cultures, DCA decreased the expression of P0 and PMP22, while it increased the levels of p75(NTR) (neurotrophin receptor), as compared with non-DCA-treated samples. DCA had modest adverse effects on neuronal and glial cell vitality, as determined by the release of lactate dehydrogenase. These results demonstrate that DCA induces a reversible inhibition of myelin-related proteins that may account, at least in part, for its clinical peripheral neuropathic effects. /Dichloroacetate/[Felitsyn N et al; J Neurochem 100 (2): 429-36 (2007)] **PEER REVIEWED** PubMed Abstract
  • ALTERNATIVE and IN VITRO TESTS: To determine whether dichloroacetate (DCA) and trichloroacetate (TCA) promote the clonal expansion of anchorage-independent liver cells in vitro, a modification of the soft agar assay (over agar assay) was utilized to quantitate growth and analyze phenotype of anchorage-independent hepatocellular colonies. Hepatocytes from naïve male B6C3F1 mice were isolated and cultured with 0-2.0 mM DCA or TCA over agar for 10 days, at which time colonies of eight cells or more were scored. Both DCA and TCA promoted the formation of anchorage-independent colonies in a dose-dependent manner. Immunocytochemical analysis using a c-Jun antibody demonstrated that colonies promoted by DCA were primarily c-Jun+, whereas TCA-promoted colonies were primarily c-Jun-. This corresponds to the differences in c-Jun immunoreactivity reported in tumors induced by DCA and TCA. Neither DCA nor TCA induced c-Jun expression in hepatocyte monolayers, indicating that these haloacetates selectively affect subpopulations of anchorage-independent hepatocyts. The latency of colony formation was decreased by the concentration of DCA, although the same number of colonies appeared after 25 days in culture at all DCA concentrations used. The plating density of hepatocytes also affected colony formation. At lower cell densities, promotion of colony formation by DCA was significantly reduced. Pretreatment of male B6C3F1 mice with 0.5 g/liter DCA in drinking water resulted in a fourfold increase in in vitro colony formation above hepatocytes isolated from naïve mice, suggesting that DCA is promoting the clonal expansion of anchorage-independent hepatocytes in vivo. Results from this study indicate that DCA and TCA promote the survival and growth of initiated cells. Furthermore, results from over agar assays reflect observations made in vivo, indicating this assay provides a valid means to investigate the mechanism by which chemicals promote clonal expansion of initiated hepatocytes.[Stauber AJ et al; Toxicol Appl Pharmacol 150 (2): 287-94 (1998)] **PEER REVIEWED** PubMed Abstract
  • GENOTOXICITY: ... The peripheral blood erythrocyte micronucleus (MN) assay and the alkaline single cell gel electrophoresis (SCG) technique /were used/ to investigate the in vivo genotoxicity of dichloroacetic acid (DCA) in bone marrow and blood leukocytes, respectively. The MN assay detects chromosome breakage and/or malsegregation, while the SCG assay detects DNA damage (e.g., single strand breaks, alkali-labile sites, crosslinking). Mice were exposed to this compound in drinking water, available ad libitum, for up to 31 weeks. ... A small but statistically significant dose-related increase in the frequency of micronucleated polychromatic erythrocytes (PCEs) /was observed/ after subchronic exposure to DCA for 9 days. In addition, at the highest dose of DCA tested (3.5 g/L), a small but significant increase in the frequency of micronucleated normochromatic erythrocytes (NCE) was detected following exposure for >/ = 10 weeks. Coadministration of the antioxidant vitamin E did not affect the ability of DCA to induce this damage, indicating that the small induction of MN by DCA was probably not due to oxidative damage. Based on the lack of any difference observed in the proportion of kinetochore-positive micronuclei between the treated and control animals, ... MN /were interpreted/ as arising from clastogenic events. The SCG technique suggested the presence of DNA crosslinking in blood leukocytes in mice exposed to 3.5 g/L DCA for 28 days. These data provide evidence that DCA may be an extremely weak inducer of chromosome damage when provided to mice in drinking water under conditions which lead to increased levels of tumors.[Fuscoe JC et al; Environ Mol Mutagen 27 (1): 1-9 (1996)] **PEER REVIEWED** PubMed Abstract
  • GENOTOXICITY: ... /It was/ previously reported that dichloroacetic acid (DCA) ... induced DNA hypomethylation in mouse liver. ... The present study ... determined the temporal association for DNA hypomethylation and cell proliferation. Female B6C3F1 mice were administered daily doses of 500 mg/kg DCA ... by gavage and sacrificed at 24, 36, 48, 72, and 96 hours after the first dose. The proliferating cell nuclear antigen-labeling index in the liver was increased at 72 and 96 hours by both DCA ... that is, at 72 hours the index was 1.00 +/- 0.21 ... and 0.095 +/- 0.016 for DCA ... and the vehicle control, respectively. The mitotic index was also significantly increased at 96 hours. The promoter region for the c-myc gene was hypomethylated only at 72 and 96 hours and not at the earlier sacrifices. Similarly, the methylation of the c-myc gene in the kidney and urinary bladder was decreased only at 72 and 96 hours. In summary, enhancement of cell proliferation and decreased methylation of the c-myc gene were first observed simultaneously at 72 hours after the start of exposure. Thus, the results support the hypothesis that DCA ... induces DNA hypomethylation by inducing DNA replication and preventing the methylation of the newly synthesized strands of DNA.[Ge R et al; J Biochem Mol Toxicol 15 (2): 100-6 (2001)] **PEER REVIEWED** PubMed Abstract
  • GENOTOXICITY: ... A series of genetic tests for mutagenicity and clastogenicity was carried out on pharmaceutical grade sodium dichloroacetate (DCA). Four types of mutagenicity test were included, with and without metabolic activation where appropriate. These studies included: (i) Salmonella and Escherichia coli mutation (Ames) test, (ii) thymidine kinase locus forward mutation in L5178Y mouse lymphoma cells, (iii) tests for chromosomal aberrations in Chinese hamster ovary cells, and (iv) and in vivo rat bone marrow erythroid micronucleus test. In each study, there was no evidence of mutagenic activity attributable to DCA. It is possible that the present test material, of pharmaceutical grade, has fewer impurities than materials studied in previous reports. These data extend, and in some cases contradict, previous published reports on DCA. /Sodium dichloroacetate/[Fox AW et al; Fundam Appl Toxicol 32 (1): 87-95 (1996)] **PEER REVIEWED** PubMed Abstract
  • GENOTOXICITY: ... Dichloroacetic acid (DCA) ... /was/ ... evaluated ... for /its/ potential to induce micronuclei and aberrations as well as mutations in L5178Y/TK +/- (-)3.7.2C mouse lymphoma cells ... DCA was weakly mutagenic, with a potency (no. of induced mutants/microgram of chemical) similar to (but less than) ethylmethanesulfonate (EMS), a classic mutagen. When /this/ ... information is combined with that from other studies, it seems reasonable to postulate that mutational events are involved in the etiology of the observed mouse liver tumors induced by DCA at drinking water doses of 0.5 to 3.5 g/L...[Harrington-Brock K et al; Mutat Res 413 (3): 265-76 (1998)] **PEER REVIEWED** PubMed Abstract
  • GENOTOXICITY: ... Dichloroacetic acid (DCA) was administered continuously at either 1.0 or 3.5 g/L in drinking water to male transgenic B6C3F1 mice harboring the bacterial lacI gene. Groups of five or six animals were killed at 4, 10 or 60 weeks and livers removed. At both 4 and 10 weeks of treatment, there was no significant difference in mutant frequency between the treated and control animals at either dose level. At 60 weeks, mice treated with 1.0 g/L DCA showed a 1.3-fold increase in mutant frequency over concurrent controls (P = 0.05). Mice treated with 3.5 g/L DCA for 60 weeks had a 2.3-fold increase in mutant frequency over the concurrent controls (P = 0.002). The mutation spectrum recovered from mice treated with 3.5 g/L DCA for 60 weeks contained G:C-->A:T transitions (32.79%) and G:C-->T:A transversions (21.31%). In contrast, G:C-->A:T transitions comprised 53.19% of the recovered mutants among control animals. Although only 19.15% of mutations among the controls were at T:A sites, 32.79% of the mutations from DCA-treated animals were at T:A sites. This is consistent with the previous observation that the proportion of mutations at T:A sites in codon 61 of the H-ras gene was increased in DCA-induced liver tumors in B6C3F1 mice. The present study demonstrates DCA-associated mutagenicity in the mouse liver under conditions in which DCA produces hepatic tumors.[Leavitt SA et al; Carcinogenesis 18 (11): 2101-6 (1997)] **PEER REVIEWED** PubMed Abstract
  • GENOTOXICITY: ...Three types of studies /were performed/ to evaluate the genotoxicity of ... dichloroacetic acid (DCA) ... In the first set of studies, which involved evaluation ... in the Microscreen prophage-induction assay, ... DCA (+S9) was genotoxic, producing 6.6-7.2 plaque-forming units/mM. This places DCA among the weakest of the > 100 chemicals that have been identified previously as inducers of prophage in this assay. In the second set of studies, which involved the evaluation of these chemicals in the vapor state in Salmonella TA100 using a Tedlar bag vaporization technique, DCA (+/-S9) ... was mutagenic, producing 3-5x increases in revertants/plate relative to the background. S9 enhanced the mutagenic potency of DCA ... The lowest effective concentrations were 50-300 p.p.m., which are similar to those for ethylene oxide and epichlorohydrin in this assay. In the third set of studies, the mutation spectra of DCA ... was determined at the base-substitution allele hisG46 of Salmonella TA100. DCA ... induced primarily G.C-->A.T transitions ...[DeMarini DM et al; Mutagenesis 9 (5): 429-37 (1994)] **PEER REVIEWED** PubMed Abstract
  • GENOTOXICITY: Contradictory results were obtained for the induction of DNA strand breaks in mammals in vivo. No effects were seen in either mouse or rat hepatic cells after single or repeated dosing, and no effects were observed in epithelial cells from spleen, stomach or duodenum after a single dose. In one study in vivo, dichloroacetic acid induced a significant decrease in DNA migration, consistent with the presence of DNA cross-linking in leukocytes in vivo, as detected by the single cell gel electrophoresis assay. Dichloroacetic acid caused mutations in male transgenic B6C3F1 mice harboring the bacterial lacI gene. In the latter study, in which mice received dichloroacetic acid in the drinking-water for 60 weeks, the mutation spectrum recovered from treated mice showed a significant decrease in GC to AT transitions (32.8% versus 53.2% for controls) and an increase in mutations at TA sites (32.79% versus 19.15% for controls).[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 386 (2004)] **PEER REVIEWED**
  • GENOTOXICITY: DNA strand breaks were not induced in mammalian cells in vitro in the absence of an exogenous metabolic activation system, but contradictory results were obtained in vivo. No effect was seen in either mouse or rat hepatic cells after single or repeated dosing, and no effects were observed in epithelial cells from spleen, stomach or duodenum after a single dose.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 284 (1995)] **PEER REVIEWED**
  • GENOTOXICITY: Dichloroacetate demonstrates low grade mutagenicity in the Ames Salmonella/mammalian microsome mutagenicity test. /Dichloroacetate/[Herbert V et al; Am J Clin Nutr 33 (6): 1179-82 (1980)] **PEER REVIEWED** PubMed Abstract
  • GENOTOXICITY: Dichloroacetic (DCA) and trichloroacetic (TCA) acids ... increase the incidence of tumors in B6C3Fl mice by 6- and 3-fold respectively. In order to understand better the mechanism by which these two compounds induce liver tumors, the incidence and spectrum of mutations in the K- and H-ras proto-oncogenes in these tumors were analyzed. DNA from spontaneous, DCA- and TCA-induced liver tumors from B6C3Fl male mice was evaluated for point mutations in exons 1, 2 and 3 of the two genes by single-stranded conformation polymorphism. Results demonstrated a similar incidence of mutations for exon 2 of H-ras in spontaneous carcinomas (58%), and in carcinomas induced by DCA 3.5 g/L (50%), 1.0 g/L (48%) and TCA 4.5 g/L (45%). Only four samples showed mutations in the other exons of H-ras or in K-ras. Sequence analysis of spontaneous tumor samples with second exon H-ras mutations revealed a change in codon 61 from CAA to AAA in 80% and CAA to CGA in 20% of tumors. In contrast, tumors with H-ras mutations from DCA-treated mice revealed a H-61 change from CAA to AAA in 21% at 3.5 g/l and 16% at 1.0 g/L. CAA to CGA was observed in 50% of tumors from mice given DCA 3.5 or 1.0 g/l, and CAA to CTA was present in 29% and 34% of the two dosage groups respectively. Interestingly, TCA showed the same mutational spectrum as the spontaneous liver tumors. The data indicates that induction of liver carcinoma by DCA and TCA involves activation of the H-ras protooncogene at a frequency similar to that observed in spontaneous tumors. However, the mechanism(s) for inducing hepatocellular carcinoma does not appear to be identical for DCA and TCA.[Ferreria-Gonzalez, et al; Carcinogenesis 16 (3): 495-500 (1995)] **PEER REVIEWED** PubMed Abstract
  • GENOTOXICITY: Dichloroacetic acid did not induce differential toxicity in DNA repair-deficient strains of Salmonella typhimurium but did induce prophage in Escherichia coli in one study. It was metagenic to Salmonella typhimurium TA100 and TA98 in single studies. Most of the mutations in 400 revertants of dichloroacetic acid treated Salmonella typhimurium TA100 cultures were GA AT transitions.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 282 (1995)] **PEER REVIEWED**
  • GENOTOXICITY: In one study in male B6C3F1 mice /of/ polychromatic erythrocytes in vivo, dichloroacetic acid induced the formation of micronuclei in two of three treatments: a dose-related increase after a 9-day exposure; no significant increase after a 28-day exposure (the value for control in that experiment was rather high (higher than after 9 days of exposure)); and a small but significant increase in the frequency of micronucleated normochromatic erythrocytes following exposure for more than 10 weeks. Coadministration of the antioxidant vitamin E did not affect the ability of dichloroacetic acid to induce this damage, indicating that the small induction of micronuclei by dichloroacetic acid was probably not caused by oxidative damage. Based on the lack of any difference observed in the proportion of kinetochore- positive micronuclei between the treated and control animals, micronuclei were assumed to arise from clastogenic events. After intravenous administration to male and female Crl:CD (SD) BR rats in vivo, dichloroacetic acid failed to induce micronuclei in bone-marrow erythrocytes in a single study. Dichloroacetic acid did not induce micronuclei in erythrocytes of new larvae in vivo.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 386 (2004)] **PEER REVIEWED**
  • GENOTOXICITY: This study examined whether the induction of single strand breaks in hepatic DNA by dichloroacetic acid (DCA) and trichloroacetic acid (TCA) depends upon peroxisome proliferation. Male B6C3F1 mice were given a single oral dose of either DCA or TCA. At varying times, between 1 and 24 hr after administration of the compounds, breaks in DNA were measured using an alkaline unwinding assay. Peroxisome proliferation was monitored at the same time intervals in a parallel experiment by measuring peroxisomal B-oxidation of (14C)palmitoyl-CoA in liver homogenates. Both DCA and TCA significantly increased breaks in DNA at 1, 2, and 4 hr post-treatment, with a return to control levels after 8 hr. No evidence for an increase in peroxisomal beta-oxidation was produced by either chemical up to 24 hr after administration.[Nelson MA et al; Toxicology 58 (3): 239-48 (1989)] **PEER REVIEWED** PubMed Abstract
  • GENOTOXICITY: Three short-term assays (SOS chromotest, Ames fluctuation test and newt micronucleus test) were performed to detect the genotoxic activity of organohalides, compounds likely to be found in chlorinated and/or ozonated drinking water: monochloro-, dichloro- and trichloroacetic acids and monobromo-, dibromo- and tribromoacetic acids. With the SOS chromotest, only three of the chemicals studied (dichloroacetic acid, dibromo- and tribromoacetic acids) were found to induce primary DNA damage in Escherichia coli PQ 37. In the Ames fluctuation test, all the compounds except monochloroacetic acid showed mutagenic activity in Salmonella typhimurium strain TA100. In these two in vitro tests, a good correlation between increasing number of substituents and decreasing mutagenicity was observed. Namely, the toxicity of brominated and chlorinated acetic acids decreased when the number of substituents increased. The newt micronucleus test detected a weak clastogenic effect on the peripheral blood erythrocytes of Pleurodeles waltl larvae for trichloroacetic acid only.[Giller S et al; Mutagenesis 12 (5): 321-8 (1997)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Acute Exposure: ...The abilities of dichloroacetate (DCA) and trichloroacetate (TCA) ...to induce oxidative stress and phagocytic activation have been studied in B6C3F1 mice. Groups of mice were administered 300 mg/kg of either DCA or TCA, po, and were sacrificed after 6 or 12 hr. Peritoneal lavage cells (PLCs) were isolated and assayed for superoxide anion (SA) production, and hepatic tissues were assayed for the production of SA, lipid peroxidation (LP), and DNA-single strand breaks (SSBs). TCA resulted in significant production of SA in the PLCs, and in the production of SA, LP, and DNA-SSBs in the hepatic tissues, 12 h after dosing, as compared with the control. DCA administration, on the other hand, resulted in significant increases in the productions of LP and DNA-SSBs in the hepatic tissues at both time points, and in SA production in PLCs and hepatic tissues, 6 h after dosing. However, DCA-induced increases in SA production in PLC and hepatic tissues declined at the 12-hr time point, reaching control level in the hepatic tissues. These results may implicate the contribution of phagocytic activation to the induction of oxidative stress in the hepatic tissues and also the role of SA production in the induction of LP and/or DNA damage in those tissues, in response to the compounds... /Dichloroacetate/[Hassoun EA, Dey S; J Biochem Mol Toxicol 22 (1): 27-34 (2008)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Acute Exposure: Dichloroacetic acid (DCA) is not very toxic when administered acutely to rodents. ... LD50s of 4.5 and 5.5 g/kg of body weight were reported/ in rats and mice, respectively, for DCA administered as the sodium salt. This is roughly in the same range as the LD50s for acetic acid. There is reason to believe that other species, most specifically the dog, may be more sensitive ...[Environmental Health Criteria 216: Disinfectants and DIsinfectant By-Products (1999) by the International Programme on Chemical Safety (IPCS) under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation and the World Health Organization. Available from, as of August 1, 2008: http://www.inchem.org/documents/ehc/ehc/ehc216.htm] **PEER REVIEWED**
  • LABORATORY ANIMALS: Acute Exposure: The compound was tested externally on the eyes of rabbits, and, according to the degree of injury observed after 24 hours, rated on a scale of 1 to 10. The most severely injurious substances have been rated 10. Dichloroacetic acid rated 10 on rabbit eyes.[Grant, W.M. Toxicology of the Eye. 3rd ed. Springfield, IL: Charles C. Thomas Publisher, 1986., p. 1029] **PEER REVIEWED**
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: ... Fifteen-day-old female mice were initiated with 25 mg/kg N-methyl-N-nitrosourea. The initiated mice were administered dichloroacetic acid (DCA) and trichloroacetic acid (TCA) DCA or TCA (20.0 mmol/L) in drinking water from age 49 days until euthanasia at age 413 days. The pathologic assessment showed that the foci of altered hepatocytes and tumors occurring in the animals promoted with DCA were eosinophilic and positive immunohistochemically for TGF-alpha, c-jun, c-myc, CYP 2E1, CYP 4A1, and glutathione S-transferase-pi (GST-pi). The DCA lesions also were essentially negative for c-fos and TGF-beta, but nontumor hepatocytes were consistently TGF-beta-positive. In contrast, tumors promoted by TCA were predominantly basophilic, lacked GST-pi, and stained variably; usually, more than 50% of the tumor hepatocytes were essentially negative for the other biomarkers. This study demonstrates some striking differences in certain molecular biomarkers of cell growth, differentiation, and metabolism between DCA and TCA. The results also suggest some potential growth signal transduction pathways that may contribute to the DCA promotion of tumors, further support the premise that these two chloroacetates promote hepatocarcinogenesis in different ways, and provide a rational basis for a similar comparison with TCE. Such a comparison should give some insight as to whether DCA, TCA, or both are playing a significant role in the murine liver carcinogenesis of the parent compound, TCE.[Latendresse JR, Pereira MA; Toxicol Pathol 25 (5): 433-40 (1997)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: ... Mice were initiated by vinyl carbamate (VC), and then promoted by dichloroacetate (DCA), trichloroacetate (TCA), carbon tetrachloride (CT), or the pair-wised combinations of the three compounds. The effect of each treatment or treatment combination on tumor number per animal and mean tumor volume was assessed in each animal. ... When administered alone in the drinking water at 0.1, 0.5 and 2 g/L, DCA increased both tumor number and tumor size in a dose-related manner. ... DCA treatment did not produce a plateau in tumor number within the experimental period /of 36 weeks/, but the numbers observed at the end of the experimental period were similar to TCA and doses of 50 mg/kg CT. The tumor numbers observed at the end of the experiment are consistent with the assumption that the administered dose of the tumor initiator, vinyl carbamate, was the major determinant of tumor number and that treatments with CT, DCA, and TCA primarily affected tumor size. The results with mixtures of these compounds were consistent with the basic hypotheses that the responses to tumor promoters with differing mechanisms are limited to additivity at low effective doses. More complex, mutually inhibitory activity was more often observed between the three compounds. At 24 weeks, DCA produced a decrease in tumor numbers promoted by TCA, but the numbers were not different from TCA alone at 36 weeks. The reason for this result became apparent at 36 weeks of treatment where a dose-related decrease in the size of tumors promoted by TCA resulted from DCA co-administration. On the other hand, the low dose of TCA (0.1 g/L) decreased the number of tumors produced by a high dose of DCA (2 g/L), but higher doses of TCA (2 g/L) produced the same number as observed with DCA alone. DCA inhibited the growth rate of CT-induced tumors (CT dose = 50mg/kg). ... These data suggest that the outcome of interactions between the mechanisms of tumor promotion vary based on the characteristics of the initiated cells. The interactions may result in additive or inhibitory effects, but no significant evidence of synergy was observed. /Dichloroacetate/[Bull RJ et al; Toxicology 199 (2-3): 169-83 (2004)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: ... The ... study examines whether biomarkers for dichloroacetate (DCA) and trichloroacetate (TCA) can be used to determine if the liver tumor response to trichloroethylene (TRI) seen in mice is completely attributable to TCA or if other metabolites, such as DCA, are involved. Previous work had shown that DCA produces tumors in mice that display a diffuse immunoreactivity to a c-Jun antibody (Santa Cruz Biotechnology, SC-45), whereas TCA-induced tumors do not stain with this antibody. ... The present study ... compared the c-Jun phenotype of tumors induced by DCA or TCA alone to those induced when they are given together in various combinations and to those induced by TRI given in an aqueous vehicle. When given in various combinations, DCA and TCA produced a few tumors that were c-Jun+, many that were c-Jun-, but a number with a mixed phenotype that increased with the relative dose of DCA. Sixteen TRI-induced tumors were c-Jun+, 13 were c-Jun-, and 9 had a mixed phenotype. Mutations of the H-ras protooncogene were also examined in DCA-, TCA-, and TRI-induced tumors. The mutation frequency detected in tumors induced by TCA was significantly different from that observed in TRI-induced tumors (0.44 vs 0.21, p < 0.05), whereas that observed in DCA-induced tumors (0.33) was intermediate between values obtained with TCA and TRI, but not significantly different from TRI. No significant differences were found in the mutation spectra of tumors produced by the three compounds. The presence of mutations in H-ras codon 61 appeared to be a late event, but ras-dependent signaling pathways were activated in all tumors. These data are not consistent with the hypothesis that all liver tumors induced by TRI were produced by TCA. /Dichloroacetate/[Bull RJ et al; Toxicol Appl Pharmacol 182 (1): 55-65 (2002)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: ... The incidence of proliferative lesions, hyperplastic nodules and altered hepatic foci, in male Fischer F344 rat liver, /was investigated/ to determine their preneoplastic potential during dichloroacetic acid (DCA) induced hepatocarcinogenesis. Immunohistochemical and image analysis methods were used to detect the expression of 6 histochemical markers of neoplastic cells; p21 ras, p39 c-jun, p55 c-fos, aldehyde dehydrogenase (ALDH), glutathione s-transferase (GST-p), and alpha fetoprotein (AFP) during DCA-induced hepatocarcinogenesis. /These/ results were consistent with our previous data and suggested that the hyperplastic nodules, rather than altered hepatic foci, is a putative preneoplastic lesion during DCA induced hepatocarcinogenesis in the male F344 rat.[Richmond RE et al; Cancer Lett 92 (1): 67-76 (1995)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: ... This study ... determined the dose response of histopathologic changes occurring in the livers of mice exposed to dichloroacetic acid (DCA) (0.05-3.5 g/L) for 26-100 weeks. Lesions were classified as foci of cellular alteration smaller than one liver lobule (altered hepatic foci; AHF), foci of cellular alteration larger than one liver lobule (large foci of cellular alteration; LFCA), adenomas (ADs), or carcinomas (CAs). Histopathologic analysis of 598 premalignant lesions revealed that (a)) each lesion class had a predominant phenotype; (b)) AHF, LFCA, and AD demonstrated neoplastic progression with time; and (c)) independent of DCA dose and length of exposure effects, some toxic/adaptive changes in non-involved liver were related to this neoplastic progression. .... Because all classes of premalignant lesions and CAs were found at both lower and higher doses, these data are consistent with the conclusion that nongenotoxic mechanisms, such as negative selection, are relevant to DCA carcinogenesis at lower doses where DCA genotoxicity has not been observed.[Carter JH et al; Environ Health Perspect 111 (1): 53-64 (2003)] **PEER REVIEWED** PubMed Abstract Full text: PMC1241306
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: ... cDNA microarray methods /were used/ for analyses of gene expression in livers of mice treated with the tumorigenic dose of 2 g/L DCA in drinking water for 4 weeks. Total RNA samples obtained from livers of the control and DCA-treated mice were evaluated for gene expression patterns with Clontech Atlas Mouse 1.2 cDNA and Atlas mouse stress/toxicology arrays, and the data analyzed with AtlasImage 2.01 and one-way ANOVA in JMP4 software. From replicate experiments, we identified 24 genes with altered expression, of which 15 were confirmed by Northern blot analysis. Of the 15 genes, 14 revealed expression suppressed two- to five-fold; they included the following: MHR 23A, cytochrome P450 (CYP) 2C29, CYP 3A11, serum paraoxonase/arylesterase 1 (PON 1), liver carboxylesterase, alpha-1 antitrypsin, ER p72, glutathione S-transferase (GST) Pi 1, angiogenin, vitronectin precursor, cathepsin D (CTSD), plasminogen precursor (contains angiostatin), prothrombin precursor and integrin alpha 3 precursor (ITGA 3). An additional gene, CYP 2A4/5, had a two-fold elevation in expression. Further, in ancillary Northern analyses of total RNA isolated from DCA-induced hepatocellular carcinomas (from earlier reported studies of mice treated with 3.5 g/L DCA for 93 weeks), many of the same genes (11 of 15) noted above showed a similar alteration in expression. In summary, ... specific genes involved in the functional categories of cell growth, tissue remodeling, apoptosis, cancer progression and xenobiotic metabolism that have altered levels of expression following exposures to DCA /were identified/. These findings serve to highlight new pathways in which to further probe DCA effects that may be critical to its tumorigenic activity.[Thai SF et al; Mutat Res 543 (2): 167-80 (2003)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: A group of 110 male B6C3F1 mice, eight weeks of age, were administered dichloroacetic acid, neutralized with sodium hydroxide, at a concentration of 0.5% in their drinking water for up to 76 weeks. Of two concurrent control groups, each consisting of 50 male mice, one was untreated and the other received corn oil at a dose of 10 ml/kg body; 10 mice in each group were killed at 76 weeks and the remainder at 96, 103, and 134 weeks (numbers not stated). At death, liver tumors measuring > or = 0.5 cm in diameter were taken for histological examination and for oncogene analysis. At the time of the terminal kill, there were 24 untreated controls, 32 corn oil controls and 89 treated animals. The number so hepatocellular adenomas per mouse in these three groups were 0.9 + or - 0.06 (8%), 0.13 + or - 0.06 (13%) and 4.98 + or - 0.38 (93%). the corresponding numbers of hepatocellular carcinomas were 0.09 + or - 0.06 (85), 0.12 + or - 0.06 (12%) and 1.73+ or - 0.17 (74%). /It was noted/ numerous foci of cellular alteration (presumed pre-neoplasic lesions) in the livers of treated mice but only rare foci in the livers of controls. No neoplasms related to treatment were found at other sites. The frequency of mutations in codon 61 of H-ras was not significantly different in the hepatocellular tumors from 64 treated mice (62%) and in those from 74 combined historical and concurrent controls (69%); however, the spectra of these mutations showed a significant decrease in AAA and an increase in CTA in the treated mice in comparison with the controls. No other H-ras mutations were found, and only one K-ras mutation was detected in tumors from the treated and concurrent control groups.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 284 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: A group of 26 male B6C3F1 mice, four weeks of age, received drinking water containing 5 g/L dichloroacetic acid (purity, > 99%) neutralized with sodium hydroxide to a pH of 6.5-7.5. A control group of 27 mice received drinking water containing 2 g/L sodium chloride. Both groups were kept for 61 weeks, at which time they were killed and necropsied. Two of 22 control mice had hepatic adenomas and none had hepatic carcinomas, whereas 25/26 mice that received dichloroacetic acid had hepatic adenomas and 21/26 had hepatocellular carcinomas (p < 0.01); Fisher's exact test.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 275 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: A group of 33 male B6C3F1 mice (initially two groups of 23 and 10 mice but analyzed as one), four weeks of age, received 0.5 g/L dichloroacetic acid (purity, > 95%; impurities unspecified; pH adjusted to 6.8-7.2 with 10 N sodium hydroxide) in distilled drinking water (pooled estimated mean dose, 88 mg/kg body weight per day) for 104 weeks; 33 control mice received distilled water only. Five mice per group were killed at 30 weeks and a further five in the control group at 60 weeks, for interim evaluation. Three control mice and four treated mice died before week 104. Of the animals killed at week 104, 15/24 treated mice and 2/20 controls had hepatocellular carcinomas (p= 0.001, Fisher's exact test); 10/24 treated mice and 1/20 control mice had hepatocellular adenomas (p= 0.005); and 18/24 treated mice and 3/20 controls had carcinomas or adenomas (p= 0.001). Two treated mice had hyperplastic liver nodules; 8/24 treated mice and 1/20 controls had hepatocellular necrosis, and 22/24 treated mice and 1/20 controls had cytomegaly.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 277 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Chronic studies are described in which male Fischer (F344) rats were exposed to dichloroacetic acid (DCA) in their drinking water. In the first study, 28 day old rats were exposed to a regimen of 0.05, 0.5 and 5.0 g/L DCA. When animals in the high dose group began to exhibit peripheral hind leg neuropathy, the dose was lowered in stages to 1 g/L. These animals were sacrificed at 60 weeks due to the severe, irreversible neuropathy and were not included in this analysis. The remaining groups of animals were treated for 100 weeks. In the second study, rats were initially exposed to 2.5 g/L DCA which was lowered to 1 g/L after 18 weeks. The mean daily concentration (MDC) of 1.6 g/L was calculated over the 103 week exposure period. Time-weighted mean daily doses (MDD) based on measured water consumption were 3.6, 40.2 and 139 mg/kg bw/day for the 0.05, 0.5 and 1.6 g/L DCA respectively. Based upon the pathologic examination, DCA induced observable signs of toxicity in the nervous system, liver and myocardium. However, treatment related neoplastic lesions were observed only in the liver. A statistically significant increase of carcinogenicity (hepatocellular carcinoma) was noted at 1.6 g/L DCA. Exposure to 0.5 g/L DCA increased-hepatocellular neoplasia, (carcinoma and adenoma) at 100 weeks. These data demonstrate that DCA is an hepatocarcinogen to the male F344 rat. Calculation of the MDD at which 50% of the animals exhibited liver neoplasia indicated that the F344 male rat (approximately 10 mg/kg bw/day) is ten times more sensitive than the B6C3F1 male mouse (approximately 100 mg/kg bw/day). A "no observed effects level' (NOEL) of 0.05 g/L (3.6 mg/kg/day) was the same as for the mouse (3.8 mg/kg/day).[DeAngelo AB et al; Toxicology 114 (3): 207-21 (1996)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Dichloroacetic acid (DCA) ... in drinking water, is hepatocarcinogenic in the B6C3F1 mouse. Previous studies have shown that DCA does not significantly alter the incidence of Ha-ras codon 61 mutations in male mouse liver carcinomas from that observed in spontaneous tumors (approximately 50% have Ha-ras mutations) but it alters the proportions of mutations that occur in Ha-ras codon 61. Twenty-two tumors were produced in female B6C3F1 mice after treatment with 3.5 g DCA per liter of drinking water over a period of 104 weeks. To detect potential Ha-ras mutations in the liver tumor tissue of female B6C3F1 mice, genomic DNA was isolated from tumors that had been frozen. The polymerase chain reaction (PCR) and single-stranded conformational polymorphism (SSCP) was used to screen tumor DNA for mutations in Ha-ras exon 2. In DNA from liver tumors in female B6C3F1 mice induced by DCA-treatment we found only one mutation in exon 2 among the 22 tumors analyzed (4.5%). Direct-sequencing of exon 2 revealed a CAA to CTA transversion in Ha-ras codon 61. The result of this study indicates that tumor formation in DCA-treated female B6C3F1 mice is, therefore, not associated with a mutationally activated Ha-ras codon 61. This result differs from previous results obtained in male B6C3F1 mice.[Schroeder M et al; Carcinogenesis 18 (8): 1675-8 (1997)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Dichloroacetic acid (DCA) and trichloroacetic acid (TCA) are mouse liver carcinogens. Methylation of the c-jun and c-myc genes, expression of both genes and DNA methyltransferase (DNA MTase) activity were determined in liver tumors initiated by N-methyl-N-nitrosourea and promoted by DCA and TCA in female B6C3F1 mice. Hypomethylated and over-expression of c-jun and c-myc genes were found in DCA- and TCA-promoted liver tumors. DNA MTase activity was increased in tumors while decreased in non-involved liver. Thus, DCA- and TCA-promoted carcinogenesis appears to include decreased methylation and increased expression of c-jun and c-myc genes in the presence of increased DNA MTase activity.[Tao L et al; Cancer Lett 158 (2): 185-93 (2000)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Dichloroacetic acid (DCA) has recently been shown to increase significantly the incidence of hepatic adenomas (HAs) and hepatocarcinomas (HCs) in male B6C3F1 mice. ... Chronic ingestion of the compound in drinking water induces primarily hyperplastic nodules (HNs) prior to the appearance of HAs and HCs. ...This study /examines/ ... the role of the HNs in the progression of DCA-induced hepatocarcinogenesis ... by detecting the expression of five different tumor markers: p21 ras, p39 c-jun, phosphotyrosine, tumor-associated aldehyde dehydrogenase and alpha-fetoprotein, all known from previous studies to be expressed more often in neoplastic liver lesions than in normal liver. Tumor marker expression was detected by immunohistochemical methods using formalin-fixed, paraffin-embedded sections of normal B6C3F1 mouse liver, and DCA-induced HNs, HAs and HCs. The results demonstrated that, except for the c-jun marker, HNs expressed the markers significantly less often than either HAs or HCs. Equal expression of c-jun occurred in any of the three lesion types. Although these results could be used to argue that no relationship existed between HNs and later-appearing HAs and HCs, those HNs that were marker positive contained small nests of marker-positive hepatocytes among a field of normally appearing unstained hepatocytes. No similar nests of marker-positive cells were detected in any area of normal liver outside the HNs. Also very few altered hepatic foci (AF) were detected with these markers or with hematoxylin and eosin, or with histochemical stains for ATPase or glucose-6-phosphatase deficiencies. These results suggested that these nests within some HNs were areas of transformed, or neoplastic hepatocytes. Phenotypic heterogeneity analysis, in which the number of tumor markers co-expressed by any given lesion was examined, confirmed a significantly greater percentage of HAs and HCs expressing multiple markers than HNs. Those HNs that expressed multiple markers, however, expressed at the same frequency as HAs and HCs and the expression was confined to the same nests of cells. Taken together, these data suggest that these nests of marker-positive cells within the HNs were neoplastic and could develop into later-appearing HAs and/or HCs. The absence of marker expression in normal liver and limited expression in the few AF indicates that the HNs may be the only significant preneoplastic lesion in DCA-induced hepatocarcinogenesis.[Richmond RE et al; Carcinogenesis 12 (8): 1383-7 (1991)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Exposure of male and female B6C3F1 mice to dichloroacetic acid at 1000 and 2000 mg/L in drinking water for up to 52 weeks induced severe cytomegaly associated with extensive accumulation of glycogen, the effects progressing to multiple focal areas of necrosis, regenerative cell division and hepatomegaly.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 281 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Groups of 10 to 40 female B6C3F1 mice, 15 days of age, were initiated with an intraperitoneal injection of 25 mg/kg bw N-methyl-N-nitrosourea (MNU). At 49 days of age, the animals received 2.0, 6.67 or 20.0 mmol/L (256, 854 or 2560 mg/L) dichloroacetic acid adjusted to pH 6.5 to 7.5 with sodium hydroxide or 20.0 mmol/L sodium chloride as a control for the sodium salt in the drinking-water. At 31 weeks, administration of 20.0 mmol/L dichloroacetic acid in the drinking-water was stopped for 12 mice that were held untreated until 52 weeks. Some mice were killed after 31 weeks of exposure and the remainder after 52 weeks. Dichloroacetic acid did not significantly increase the incidence or multiplicity of hepatocellular adenocarcinomas. The high dose of dichloroacetic acid increased the incidence of hepatocellular adenomas in MNU-initiated mice from 0/10 to 5/10 (50%) at 31 weeks and from 7/40 (17.5%) to 19/26 (73.1%) at 52 weeks. The multiplicity of hepatocellular adenomas was increased (p < 0.01) from 0.00 to 1.80 +/- 0.83 and from 0.28 +/- 0.11 to 3.62 +/- 0.70 at 31 and 52 weeks, respectively. The two lower doses of dichloroacetic acid did not significantly increase tumor incidence or multiplicity. The high dose of dichloroacetic acid also promoted MNU-initiated altered hepatocyte foci. The foci and tumors promoted by dichloroacetic acid were eosinophilic and contained glutathione S-transferase-pi. When exposure to dichloroacetic acid was stopped after 31 weeks, the tumors that it had promoted appeared to regress (1.80 +/- 0.83 at week 31 and 0.69 +/- 0.26 at week 52).[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 367 (2004)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Groups of 50 male B6C3F1 mice, four weeks old, were given 0.05, 0.5, or 5 g/L dichloroacetic acid (purity, > 99%; adjusted to pH 6.8-7.2 by the addition of 10 N sodium hydroxide) in the drinking water. A control group of 50 mice was given drinking water containing 2 g/L sodium chloride. In a second experiment, groups of 50 male B6C3F1 mice were given drinking water containing either 3.5 g/L dichloroacetic acid or 1.5 g/L acetic acid (control group) in order to examine the metabolic appropriateness of an alternative control group. Interim kills of five mice were made in all treatment groups at four, 15, 30, and 45 weeks, except in the group given 3.5 g/L dichloroacetic acid. After 60 weeks of treatment, nine mice treated with 2 g/L saline or with 0.05 or 0.5 g/L dichloroacetic acid and 30 mice given 5.0 g/L dichloroacetic acid were killed. The remaining animals were killed at 75 weeks. In the second experiment, 12 mice receiving 3.5 g/L dichloroacetic acid and 10 mice given acetic acid were killed at 60 weeks. (The fate of the remaining mice in these two groups is not described) Drinking water intake and final body weight were lower in the groups receiving 3.5 or 5.0 g/L dichloroacetic acid than among their respective controls; there was no difference in survival. Proliferative lesions of the liver were classified as hyperplastic nodules, hepatocellular adenomas or hepatocellular carcinomas; the prevalence of the two tumors types was reported only as percentages on the basis of the number of animals examined. Hyperplastic nodules occurred mainly among animals receiving dichloroacetic acid; the prevalence rates (presented graphically) at 60 weeks were 58% among those given 3.5 g/L and 83% for those given 5.0 g/L. Hepatocellular carcinomas were first observed at 30 weeks in mice at 3.5 g/L. At 60 weeks, the group given 5.0 g/L dichloroacetic acid had prevalences of 80% hepatic adenomas and 83% hepatocellular carcinomas (p < 0.001). In contrast, the prevalences of hepatic adenomas and carcinomas (combined) were 11.1% in the group given 0.5 g/L dichloroacetic acid and 24.1% in that given 0.05% g/L; these values were not significantly different from that in the saline controls (7.1%). No liver tumors were found in 10 controls given acetic acid and killed at 60 weeks.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 276-7 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Groups of male B6C3F1 mice (N = 50) were provided drinking water containing 2 g/liter sodium chloride (control) and 0.05, 0.5, and 5 g/liter dichloroacetic acid (DCA). Treatment of 30 animals in each group was carried out to 60 or 75 weeks. In a separate experiment, mice exposed to 3.5 g/liter DCA and the corresponding acetic acid control group were killed at 60 weeks. Groups of 5 mice were killed at 4, 15, 30, and 45 weeks. Time-weighted mean daily doses of 7.6, 77, 410, and 486 mg/kg/day were calculated for 0.05, 0.5, 3.5, and 5 g/liter DCA treatments. Animals exposed to 3.5 and 5 g/liter DCA had final body weights that were 87 and 83%, respectively, of the control value. Relative liver weights of 136, 230, and 351% of the control value were measured for 0.5, 3.5, and 5 g/liter, respectively. At 60 weeks mice receiving 5.0 g/liter DCA had a 90% prevalence of liver neoplasia with a mean multiplicity of 4.50 tumors/animal. Exposure to 3.5 g/liter DCA for 60 weeks resulted in a 100% tumor prevalence with an average of 4.0 tumors/animal. The prevalence of liver neoplasia and tumor multiplicity at 60 and 75 weeks in the 0.05 g/liter DCA (24.1%; 0.31 tumors/animal) and in the 0.5 g/liter group (11.1%; 0.11 tumors/animal) did not differ significantly from the control value (7.1% and 0.07 tumors/animal). No liver tumors were found in the group treated with acetic acid. Hyperplastic nodules were seen in the 3.5 (58%; 0.92/animal) and 5 g/liter DCA groups (83%; 1.27/animal). There was a significant positive dose-related trend in the age-adjusted prevalence of liver tumors. These data confirm the hepatocarcinogenicity of DCA administered in the drinking water to male B6C3F1 mice for 60 weeks. The results together with those in an earlier report from this laboratory suggest, for the conditions under which these assays were conducted, a threshold concentration of at least 0.5 g/liter followed by a steep rise to a maximum tumor incidence at 2 g/liter DCA.[DeAngelo AB et al; Fundam Appl Toxicol 16 (2): 337-47 (1991)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Groups of male and female B6C3F1 mice, 37 days old, received dichloroacetic acid in drinking water neutralized to pH 6.8-7.2 with sodium hydroxide) for up to 52 weeks, at which time the experiment was terminated. A group of 11 male mice received a dose of 1 g/L for 52 weeks, 24 male mice received 2.0 g/L for 52 weeks, and a further group of 11 males received 2.0 g/L for 37 weeks and then water alone until week 52. Two groups of 35 and 11 male control mice were kept until the end of the experiment. Groups of 10 female mice received either 0 or 2.0 g/l dichloroacetic acid for 52 weeks. Livers and kidneys were weighted and examined macroscopically. Microscopic examination was undertaken only of lesions found in the livers of 35 male control mice, the 11 male mice treated with 2.0 g/L dichloroacetic acid for 37 weeks and other groups (numbers unspecified) chosen at random. The lesions were classified histologically as hyperplastic nodules, adenomas or hepatocellular carcinomas. The incidences of these lesions were increased in mice receiving 2 g/L dichloroacetic acid. Only hyperplastic nodules and adenomas were found in mice treated for 37 weeks, and only hyperplastic nodules were observed in 3/10 treated female mice (no further details reported). Other pathological signs seen at 37 or 52 weeks in males and females treated with dichloroacetic acid included cytomegaly, massive accumulation of glycogen and focal necrotic lesions.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 276 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Hepatic tumor promoting activity was determined for dichloroacetic acid (DCA) and trichloroacetic acid (TCA) in female B6C3F1 mice initiated on day 15 of age with 25 mg/kg N-methyl-N-nitrosourea (MNU). The mice were administered the chloroacetic acids in drinking water starting at 7 weeks of age and continuing until sacrificed 31 or 52 weeks later. Both chloroacetic acids promoted MNU-initiated foci and tumors, however their concentration-response relationships differed being exponential and linear for DCA or TCA, respectively. Lesions promoted by DCA but not by TCA, regressed upon termination of exposure at 31 weeks. Foci and tumors promoted by DCA were eosinophilic and contained glutathione S-transferase-pi(GST-pi), while TCA promoted basophilic tumors lacking GST-pi. Hence, tumor promotion by DCA and TCA appeared to differ both with respect to their concentration-response relationships and to the characteristics of precancerous lesions and tumors.[Pereira MA, Phelps JB; Cancer Lett 102 (1-2): 133-41 (1996)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Hepatic tumor promoting activity was determined for mixtures of dichloroacetic acid (DCA) and trichloroacetic acid (TCA) in female B6C3F1 mice initiated on day 15 of age with 25 mg/kg N-methyl-N-nitrosourea. The mice received in their drinking water from 6 to 50 weeks of age either DCA (7.8, 15.6, or 25 mmol/L) with/without 6.0 mmol/L TCA or TCA (6.0 or 25 mmol/L) with/without 15.6 mmol/L DCA. Proliferative lesions (foci of altered hepatocytes and hepatocellular adenomas) promoted by TCA increased linearly with its concentration and were predominantly basophilic and negative for glutathione S-transferase-pi (GST-pi), while those promoted by DCA increased exponentially with its concentration and were eosinophilic and positive for GST-pi. The promoting activity of DCA and TCA in mixtures was at least additive. The proliferative lesions resulting from exposure to the mixtures were predominately similar to those promoted by DCA, ie, contained eosinophilic and GST-pi-positive hepatocytes.[Pereira MA et al; Cancer Lett 115 (1):15-23 (1997)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Hypomethylation of DNA and the insulin-like growth factor-II (IGF-II) gene was determined in dichloroacetic acid (DCA) and trichloroacetic acid (TCA) promoted /mouse/ liver tumors ... initiated by N-methyl-N-nitrosourea ... By dot-blot analysis using an antibody for 5-methylcytosine, the DNA in DCA- and TCA-promoted tumors was demonstrated to be hypomethylated. The methylation status of 28 CpG sites in the differentially methylated region-2 (DMR-2) of mouse IGF-II gene was determined. In liver, 79.3 +/- 1.7% of the sites were methylated, while in DCA- and TCA-treated mice, only 46.4 +/- 2.1% and 58.0 +/- 1.7% of them were methylated and 8.7 +/- 2.6% and 10.7 +/- 7.4% were methylated in tumors. The decreased methylation found in liver from mice exposed to DCA or TCA occurred only in the upstream region of DMR-2, while in tumors it occurred throughout the probed region. mRNA expression of the IGF-II gene was increased in DCA- and TCA-promoted liver tumors but not in non-involved liver from DCA- and TCA-exposed mice. The results support the hypothesis that DNA hypomethylation is involved in the mechanism for the tumorigenicity of DCA and TCA.[Tao L, et al; Toxicology 196 (1-2): 127-36 (2004)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: In eight studies, neurtalized dichloroacetic acid administered in the drinking water to male and/or female mice increased the incidences of hepatocellular adenomas and/or carcinomas. Following oral administration of dichloroacetic acid in the drinking-water to male rats, an increased incidence of hepatocellular carcinomas was found at a dose that decreased body weight and an increase in the combined incidence of adenomas and carcinomas was found at a lower dose. When administered in the drinking-water, dichloroacetic acid promoted hepatocellular carcinomas in carcinogen-initiated male and female mice in three studies.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 391 (2004)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Male B6C3F1, mice were exposed to dichloroacetic acid (DCA) in the drinking water in order to establish a dose response for the induction of hepatocellular cancer and to examine several modes of action for the carcinogenic process. Groups of animals were exposed to control, 0.05, 0.5, 1, 2, or 3.5 g/L DCA in the drinking water for 90-100 wk. Mean daily doses (MDD) of 8, 84, 168, 315, and 429 mg/kg/d of DCA were calculated. The prevalence (percent of animals) with hepatocellular carcinoma (HC) was significantly increased in the 1 g/L (71%), 2 g/L (95%), and 3.5 g/L (100%) treatment groups when compared to the control (26%). HC multiplicity (tumors/animal) was significantly increased by all DCA treatments-0.05 g/L (0.58), 0.5 g/L (0.68), 1 g/L (1.29), 2 g/L (2.47), and 3.5 g/L (2.90)-compared to the control group (0.28). Based upon HC multiplicity, a no-observed-effect level (NOEL) for hepatocarcinogenicity could not be determined. Hepatic peroxisome proliferation was significantly increased only for 3.5 g/L DCA treatment at 26 wk. and did not correlate with the liver tumor response. The severity of hepatotoxicity increased with DCA concentration. Below 1 g/L, hepatotoxicity was mild and transient as demonstrated by the severity indices and serum lactate dehydrogenase activity. An analysis of generalized hepatocyte proliferation reflected the mild hepatotoxicity and demonstrated no significant treatment effects on the labeling index of hepatocytes outside proliferative lesions. Consequently, the induction of liver cancer by DCA does not appear to be conditional upon peroxisome induction or chemically sustained cell proliferation. Hepatotoxicity, especially at the higher doses, may exert an important influence on the carcinogenic process. /Dichloroacetate/[DeAngelo AB et al; J Toxicol Environ Health A 58 (8): 485-507 (1999)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Male and female B6C3F1 mice were administered dichloroacetate (DCA) and trichloroacetate (TCA) in their drinking water at concentrations of 1 or 2 g/L for up to 52 weeks. Both compounds induced hepatoproliferative lesions (HPL) in male mice, including hepatocellular nodules, adenomas and hepatocellular carcinomas within 12 months. The induction of HPL by TCA was linear with dose. In contrast, the response to DCA increased sharply with the increase in concentration from 1 to 2 g/L. Suspension of DCA treatment at 37 weeks resulted in the same number of HPL at 52 weeks that would have been predicted on the basis of the total dose administered. However, none of the lesions in this treatment group progressed to hepatocellular carcinomas. Conversely, the yield of HPL at 52 weeks when TCA treatment was suspended at 37 weeks was significantly below that which would have been predicted by the total dose administered. In this case, 3 of 5 remaining lesions were hepatocellular carcinomas. Throughout active treatment DCA-treated mice displayed greatly enlarged livers characterized by a marked cytomegaly and massive accumulations of glycogen in hepatocytes throughout the liver. Areas of focal necrosis were seen throughout the liver. TCA produced small increases in cell size and a much more modest accumulation of glycogen. Focal necrotic damage did not occur in TCA-treated animals. TCA produced marked accumulations of lipofuscin in the liver. Lipofuscin accumulation was less marked with DCA. These data confirm earlier observations that DCA and TCA are capable of inducing hepatic tumors in B6C3F1 mice and argue that the mechanisms involved in tumor induction differ substantially between these two similar compounds... /Dichloroacetate/[Bull RJ et al; Toxicology 63 (3): 341-59 (1990)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: Mice were treated with 2 g/L dichloroacetic acid (DCA) in drinking water for 4 weeks. Total RNAs were obtained from livers of both control and treated mice for analysis. Of approximately 48,000 bands on the differential display gels representing an estimated 96% of RNA species, 381 showed differences in intensity. After cloning and confirmation by both reverse-northern and northern analyses, six differentially expressed genes were found. The expression of five of these genes was suppressed in the DCA-treated mice while one was induced. After sequencing, four genes were identified and two were matched to expressed sequence tags through the BLAST program. These genes are alpha-1 protease inhibitor, cytochrome b5, stearoyl-CoA desaturase and carboxylesterase. Stearoyl-CoA desaturase was induced approximately 3-fold in the livers of DCA-treated mice and the other three genes were suppressed approximately 3-fold. Stearoyl-CoA desaturase, cytochrome b5 and carboxylesterase are endoplasmic reticulum membrane-bound enzymes involved in fatty acid metabolism. The expression pattern of four of these genes was similar in DCA-induced hepatocellular carcinomas and the 4 week DCA-treated mouse livers. The expression of stearoyl-CoA desaturase and one of the unidentified genes returned to control levels in the carcinomas. Understanding the roles and interactions between these genes may shed light on the mechanism of DCA carcinogenesis.[Thai SF et al; Carcinogenesis 22 (8): 1317-22 (2001)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: The ... study was designed to determine the extent to which the tumorigenic effects of dichloroacetic acid (DCA) could be explained by its effect on tumor growth rates (ie, tumor promoting activity). In vivo magnetic resonance imaging (MRI) allowed accurate determination of growth rates of individual lesions in mice that had been treated with DCA in drinking water at 2 g/L. Out of thirty treated mice, ten were found to have hepatic tumors detectable by MRI at 48 weeks of treatment. These tumor-bearing animals were assigned to two groups matched on the size of lesions observed by in vivo MRI. Treatment with DCA continued in one group of five mice and was stopped in the other. For both groups, tumor growth rates were determined by measuring changes in size of all lesions greater than 1 cu mm in volume during a 14-day period. Removal of DCA treatment resulted in growth rates that could not be distinguished from zero across all lesion sizes represented in the sample ... /It was concluded that/ the effects of DCA on the division and/or death rates of spontaneously initiated cells can account for the predominance of small lesions in DCA-treated animals.[Miller JH et al; Toxicology 145 (2-3): 115-25 (2000)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: The chlorinated acetaldehydes, chloral hydrate (CH) and 2-chloroacetaldehyde (CAA) ... /were examined for/ ...carcinogenicity ... /in/ chronic bioassays conducted with male B6C3F1 mice exposed to levels of 1 g/L CH and 0.1 g/L CAA via the drinking water for 104 weeks. Distilled water (H2O) served as the untreated control and dichloroacetic acid (DCA; 0.5 g/L), another chlorine disinfection by-product, was included. The mean daily ingested doses were approximately 166 mg/kg/day for CH, 17 mg/kg/day for CAA, and 93 mg/kg/day for DCA. Evaluations included mortality, body weight, organ weights, gross pathology, and histopathology. The primary target organ was the liver as the organ weights and pathological changes in the other organs (spleen, kidneys, and testes) were comparable between the treated groups and the H2O control group. Liver weights were increased for all three test chemicals at the terminal euthanasia with the greatest increase seen in the CH and DCA groups. Hepatocellular necrosis was induced by all three test chemicals, and it was also most prevalent and severe in the CH and DCA groups. A significant increase in the prevalence of liver tumors was seen for all three chemicals. The strongest response was with DCA, in which 63% of the 104-week survivors had hepatocellular carcinomas (carcinomas) and 42% possessed hepatocellular adenomas (adenomas) and the combined prevalence for carcinomas plus adenoma was 75%....[Daniel FB et al; Fundam Appl Toxicol 19 (2): 159-68 (1992)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: The concentration-response relationships for the hepatocarcinogenic activity of dichloroacetic acid (DCA) and trichloroacetic acid (TCA), two contaminants of finished drinking water, were determined in female B6C3F1 mice. Dicholoracetic acid or trichloroacetic acid at 2.0, 6.67, or 20.0 mmol/liter was administered to the mice in the drinking water starting at 7 to 8 weeks of age and until sacrifice after 360 or 576 days of exposure. The relationships of the yield of foci of altered hepatocytes, hepatocellular adenomas, and hepatocellular carcinomas to the concentration of DCA and TCA in the water were best described by second-order and linear regressions, respectively. The liver-to-body weight ratio increased linearly for both DCA and TCA, as did the vacuolization of the liver induced by DCA. The foci of altered hepatocytes and tumors in the animals treated with DCA were predominantly eosinophilic and contained glutathione S-transferase-pi (GST-pi, over 80% of the lesions), while the tumors induced by TCA were predominantly basophilic and lacked GST-pi, including all 11 hepatocellular carcinomas. Therefore, the carcinogenic activity of DCA AND TCA appeared to differ both with respect to their dose- response relationship and to the characteristics of precancerous lesions and tumors.[Pereira MA; Fundam Appl Toxicol 31 (2): 192-9 (1996)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: The expression of c-myc and c-H-ras in hyperplastic nodules and hepatocellular carcinomas induced in male B6C3F1 mice after chronic administration of dichloroacetate (DCA) and trichloroacetate (TCA) was studied using in situ hybridization. Expression of c-myc and c-H-ras mRNA was increased in both nodules and carcinomas relative to surrounding tissue and tissues obtained from control animals. Myc expression was similar in hyperplastic nodules and carcinomas induced by DCA, but was significantly higher in TCA-induced carcinomas than in hyperplastic nodules and carcinomas produced by DCA. In carcinomas from animals whose TCA treatment was suspended at 37 weeks, c-myc expression remained high relative to control and surrounding liver tissue at 52 weeks. In contrast, the expression of c-H-ras was consistently elevated in carcinomas from both treatments relative to hyperplastic nodules and non-tumor tissue. Within carcinomas from both treatments, focal areas could be located which expressed even higher levels of c-myc. This heterogeneity was not observed in carcinomas hybridized to c-H-ras-probes. These data suggest that elevated expression of c-H-ras and c-myc might play an important role in the development of hepatic tumors in B6C3F1 mice. Elevated expression of c-H-ras was closely associated with malignancy. Increased c-myc expression does not seem necessary for progression to the malignant state. On the other hand, the increased expression of c-myc appears related to the earlier progression of TCA-induced tumors to the malignant state. /Dichloroacetate/[Nelson MA et al; Toxicology 64 (1): 47-57 (1990)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity: The toxicological relevance of the inhibition of glutathione-S-transferase biotransformation by dichloroacetic acid (DCA) in different species is not entirely clear. For instance, ... Fischer (F344) rats were more sensitive than B6C3F1 mice with regard to DCA-induced hepatocarcinogenicity based on the mean daily doses at which 50% of the animals exhibited liver neoplasia. However, the rates of DCA biotransformation were much greater in mice than rats. Accordingly, /it was/ concluded that the carcinogenicity of DCA does not appear to be directly related to its glutathione-S-transferase-dependent biotransformation. ... Differences in carcinogenicity may be related to tyrosine metabolites that accumulate when GSTZ is inhibited rather than DCA metabolites. The study authors proposed that DCA concentrations that inhibit GSTZ also increase the concentration of MAA and its decarboxylated end product, maleylacetone, both of which are postulated to be alkylating agents and are linked to the mechanism for carcinogenesis for those that suffer from hereditary tyrosinemia I.[U.S. EPA; Toxicological Review of Dichloroacetic Acid (CAS No. 79-43-6) In Support of Summary Information on the Integrated RIsk Information System EPA 635/R-03/007 p.11 (August 2003) Available from a database querie of www.epa.gov/iris as of August 1, 2008] **PEER REVIEWED**
  • LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity:...This study ... determined the ability /of bromodichloromethane (BDCM), chloroform, dibromoacetic acid (DBA), dichloroacetic acid (DCA), and trichloroacetic acid (TCA)/ to cause renal DNA hypomethylation. B6C3F1 mice were administered DCA or TCA concurrently with/without chloroform in their drinking water for 7 days. In male, but not female mouse kidney, DCA, TCA, and to a lesser extent, chloroform decreased the methylation of DNA and the c-myc gene. Coadministering chloroform increased DCA but not TCA-induced DNA hypomethylation. DBA and BDCM caused renal DNA hypomethylation in both male B6C3F1 mice and Fischer 344 rats. ... In mouse liver, methionine prevented DCA- and TCA-induced hypomethylation of the c-myc gene. To determine whether it would also prevent hypomethylation in the kidneys, male mice were administered methionine in their diet concurrently with DCA or TCA in their drinking water. Methionine prevented both DCA- and TCA-induced hypomethylation of the c-myc gene. The ability of the DBPs to cause hypomethylation of DNA and of the c-myc gene correlated with their carcinogenic and tumor promoting activity in mouse and rat kidney, which should be taken into consideration as part of their risk assessment. That methionine prevents DCA- and TCA-induced hypomethylation of the c-myc gene would suggest it could prevent their carcinogenic activity in the kidney.[Tao L et al; Toxicol Sci 87 (2): 344-52 (2005)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: ... One of the important classes of disinfection by-products (DBPs) is the haloacetic acids. /It was/ ... previously shown that the haloacetic acids (HAs), dichloro (DCA), dibromo (DBA) and bromochloro (BCA) acetic acid are developmentally toxic in mouse whole embryo culture. ... This study explores the question of developmental toxicity interactions between these compounds. Gestational day (GD) 9.5 rat embryos were exposed to various concentrations of the three HAs (singly or in combination) for 48 hr and then evaluated for dysmorphology. The embryonic effects from exposure to the single compounds and mixtures were evaluated using developmental score (DEVSC) as the parameter of comparison. Concentrations of individual compounds and mixtures were chosen (based on a dose-additivity model) which were predicted to produce scores 10 or 20% lower than control levels. Evaluations were performed on all possible combinations of the three HAs. The HAs were dysmorphogenic and resulted in primarily rotation and heart defects and to a lesser extent prosencephalic, visceral arch, and eye defects. The percent anomalies in the rat were comparable to those previously published for the mouse at comparable toxicant concentration. There was a low incidence of neural tube defects in the rat following exposure to the HAs. The rat neural tube appeared less sensitive to the HAs than did the mouse resulting in a higher rate of neural tube dysmorphology in the mouse. Following exposures to BCA and DBA, alone and in combination, there was a significant incidence of delayed embryonic caudal development with apparent normal development anterior to the second visceral arch. The developmental scores for embryos exposed to combinations of the three compounds, when compared to scores for embryos exposed to the single compounds, indicated that the dose-additivity model adequately predicted the observed toxicity and that the developmental toxicity of these water disinfection by-products appears to be additive in whole embryo culture (WEC).[Andrews JE et al; Reprod Toxicol 19 (1): 111-6 (2004)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: ... 3-6 somite CD-1 mouse embryos were exposed to acetic acid (AA), or mono(M), di(D), and tri(T) substituted chloro(C) or bromo(B)-acetic acids(A) (e.g. DCA = dichloroacetic acid) in whole embryo culture and the morphological effects were evaluated. Conceptuses exposed to these agents for 24 hours exhibited malformations. Neural tube defects ranged from prosencephalic hypoplasia to non-closure throughout the cranial region. Other craniofacial defects included optic, otic and pharyngeal arch dysmorphogenesis. Benchmark concentrations (BC) for a 5% increase in neural tube defects for the studied chemicals in order of increasing potency are DCA (2452 uM) less than AA (1888 uM) less than TBA (1403 uM) less than TCA (1336 uM) less than DBA (162 uM) less than MCA (91.5 uM) less than MBA (2.68 uM). Quantitative structure-activity relationships were derived from these data and other (iodo(I) and fluoro(F)) haloacetic acid data not presented (MIA, MFA, DFA, TFA). The best regression was derived by excluding acetic acid (n = 10) and relating log(1/BC) to Elumo and pKa with r = 0.96, adj r2 = 0.90. These studies indicate that all of the haloacetates can directly alter development and there is a wide range of concentrations that produce dysmorphogenesis.[Rogers EH et al; Teratol 51 (3):195 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: ... Previous investigations in this laboratory showed that dichloroacetic acid (DCA) given to pregnant Long-Evans rats on gestation days 6-15 (plug=0) at 140, 400, 900, 1400 or 2400 mg/kg/day caused malformations principally in the cardiovascular system. Since a no observed adverse effect level (NOAEL) was not demonstrated, ... an additional study using a lower dose of 14 mg/kg and repeated two other doses, 140 and 400 mg/kg /was conducted/. No animals died during treatment, but as seen in the previous study, maternal weight gain was reduced at 140 and 400 mg/kg/day. The relative weights of liver, spleen and kidney were increased at all dose levels. Mean fetal weight and length were decreased in the groups treated with 400 mg/kg DCA but not in controls and the lower dose groups. The patterns of malformations seen in this study were similar to those observed in the preceding study with a defect between the ascending aorta and right ventricle being predominant. The incidence of the defect was significantly increased only at the 400 mg/kg dose level, but total soft tissue malformations were significantly elevated at 140 mg/kg. /It was concluded/ that the 14 mg/kg dose of DCA is a NOAEL for developmental toxicity in the rat.[Randall JL et al; Teratol 43 (5): 454 (1991)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: ... Since the half-lives of the haloacetic acids (HAAs) in vivo are typically <8 hr, the developmental effects of short-term exposures to dihaloacetates were evaluated. Gestation day 8 (3-6 somite pairs) CD-1 mouse conceptuses were exposed to 11,000 uM dichloroacetic acid (DCA), 300 uM dibromoacetic acid (DBA) or 300 uM bromochloroacetic acid (BCA) for culture periods of 1, 3, 6 or 26 hr. Following 1, 3 or 6 hr of exposure to HAAs, conceptuses were transferred to control medium to complete a 26-hr culture period. The amounts of HAAs present in embryos after 1, 3 and 6 hr of exposure were determined. Increased incidences of dysmorphic embryos were produced by 6 or 26-hr exposures to DCA; a 26-hr exposure to DBA; or 3, 6 or 26-hr exposures to BCA. The dysmorphology produced was dependent upon the length of exposure and chemical. The embryonic concentration of each HAA (104.5, 2.5 and 2.6 pmol/ug protein for DCA, DBA and BCA, respectively) was reached by 1 hr of exposure and did not change at the subsequent time points examined. The current studies demonstrate that BCA is more potent than DBA or DCA at disrupting embryogenesis since shorter exposures alter morphogenesis. Since the embryonic HAA concentrations were the same at the three time points measured, the time-dependence in dysmorphogenesis does not appear to be a simple function of increasing embryonic concentration of these chemicals...[Hunter ES 3rd et al; Reprod Toxicol 22 (3): 443-8 (2006)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: ... The developmental toxicity of dichloroacetic acid (DCA) has been determined in zebrafish (Danio rerio) embryos. Embryos were exposed to different concentrations (4, 8, 16, and 32 mM) of the compound at the 4 hr postfertilization (hpf) stage of development, and were observed for different developmental toxic effects at 8, 24, 32, 55, 80, and 144 hpf. Exposure of embryos to 8-32 mM of DCA resulted in significant increases in the heart rate and blood flow of the 55 and 80 hpf embryos that turned into significant decreases at the 144 hpf time point. At 144 hpf, malformations of mouth structure, notochord bending, yolk sac edema and behavioral effects including perturbed swimming and feeding behaviors were also observed. DCA was also found to produce time- and concentration-dependent increases in embryonic levels of superoxide anion (O2*-) and nitric oxide (NO), at various stages of development. The results of the study suggest that DCA-induced developmental toxic effects in zebrafish embryos are associated with production of reactive oxygen species in those embryos.[Hassoun E et al; J Biochem Mol Toxicol 19 (1): 52-8 (2005)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: Dichloroacetic acid (DCA) ... may occur in treated water at levels exceeding 100 ug/L. Previous studies revealed teratogenic effects, particularly heart malformations, at high doses (900-2,400 mg/kg given on days 6-15 of pregnancy). In a series of three studies, groups of 7-10 Long-Evans rats were dosed with 1,900 mg/kg of DCA on days 6-8, 9-11, or 12-15; with 2,400 mg/kg on days 10, 11, 12, or 13; and with 3,500 mg/kg on days 9, 10, 11, 12, or 13, in an attempt to determine the most sensitive period and further characterize the heart defect. In a fourth study, six dams were treated with 1,900 mg/kg of DCA days 6-15 of pregnancy, and 56 fetuses were harvested for light microscopy of the heart. Eight control fetuses from four litters were also examined. No heart malformations were seen in the groups treated with 1,900 mg/kg DCA days 6-8 but were present in the group treated on days 9-11 and 12-15, with the higher incidence occurring on days 12-15. Single doses of 2,400 mg/kg DCA given on days 10, 11, 12, or 13 resulted in a much lower incidence of cardiac malformations, which occurred only on days 10 and 12. The high dose of DCA (3,500 mg/kg) did not increase the incidence of heart defects but showed that dosing on day 9 as well as on days 10 and 12 would produce the defect. The defects seen were characterized as high interventricular septal defects (H-IVSD). Light microscopy showed that the defect was caudal to the semilunar valves, with the anterior right wall of the aorta communicating with the right ventricle. Another aspect of the defect is at the level of the semilunar valves, with the right cusp or sinus of Valsalva in communication with the right ventricle...[Epstein DL et al; Teratology 46 (3): 225-35 (1992);Comment in: Teratology 47 (6): 527-9 (1993)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: Dichloroacetic acid and its metabolites accumulate in rat fetuses after treatment of the dam. The main effect of maternal doses of 140-2400 mg/kg body weight per day on days 6-15 of gestation was altered development of the heart and major vessels and less frequently, the kidneys and the orbits of the eyes.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 282 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: Haloacetic acids (HAs) are embryotoxic contaminants commonly found in drinking water. The mechanism of HA embryotoxicity has not been defined, but may be mediated in part by protein kinase C (PKC) inhibition. This study was conducted to evaluate the pathogenesis of HA embryotoxicity, and to compare these data with those from specific (Bis I) and non-specific (staurosporine) inhibitors of PKC. Embryos were incubated for varying times with several HAs, Bis I, staurosporine, or Bis V (a negative control). Cell cycle analysis was performed by flow cytometry following nuclear staining with propidium iodide; apoptosis was evaluated by fluorescence microscopy following LysoTracker staining. At concentrations producing 100% embryotoxicity with no embryolethality, only staurosporine perturbed the cell cycle. However, flow cytometry revealed accumulation of sub-G1 events (an apoptotic indicator) across time with bromochloroacetic acid, dichloroacetic acid, and staurosporine, but not dibromoacetic acid, Bis I, or Bis V. Sub-G1 events were particularly prominent in the head region, and remained at control levels in the heart. LysoTracker staining confirmed a similar pattern of apoptosis in the intact embryo; BCA and DCA produced intense staining in the prosencephalon, with virtually no staining in the heart. These data indicate that while cell-cycle perturbation may not mediate the pathogenesis of HA embryotoxicity, these agents do induce embryonic apoptosis. In addition, the lack of Bis I-induced apoptosis indicates that PKC inhibition is unlikely to be the sole mediator of HA embryotoxicity.[Ward KW et al; Toxicol Sci 53 (1): 118-26 (2000)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: Long term administration of dichloroacetic acid orally at up to 72 mg/kg body weight per day to dogs and 80.5 mmol/L (10 g/L) in drinking water to rats (calculated dose, 1100 mg/kg body weight per day) for 90 days induced testicular toxicity in both species, with degeneration of the seminiferous epithelium. Earlier studies in rats, including one with a similar dose (1100 mg/kg body weight per day for seven days), showed normal testicular histopathology and sperm production. In male Long-Evans rats given 0, 31.3, 62.5, or 125 mg/kg body weight per day by gavage for 10 weeks, toxic effects were seen on the male reproductive accessory organs (preputial glands and epididymes) and sperm at 31.3 or 62.5 mg/kg body weight, whereas toxic effects on the testis and a reduction in late-step spermatid head count were observed only in the group given the highest dose. The number of viable implants on day 14 of gestation after an overnight mating with unexposed controls was decreased only in group at the high dose.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 282 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: Male Long-Evans rats with 0, 31.25, 62.5, or 125 mg dichloroacetate (sodium salt) (DCA)/kg/day by oral gavage for 10 weeks. Compared to controls, preputial gland and epididymis weights were reduced at 31.25 mg/kg, body and liver weights at 62.5 mg/kg, and accessory organ weights at 125 mg/kg. Epididymal sperm counts were reduced and sperm morphology was impacted at the 62.5 and 125 mg/kg doses levels. Histologic examination of the testis and epididymis revealed inhibited spermiation in testes at the 125 mg/kg dose level. Computer-assisted sperm motion analysis revealed reductions in percentage motile sperm, curvilinear and straight-line velocity, linearity, and amplitude of lateral head displacement at both the 62.5 and the 125 mg/kg dose levels. In the assessment of fertility after an overnight mating, the number of viable implants on Day 14 of gestation was decreased only in the highest dose group. These studies demonstrate adverse effects of NaDCA treatment on the rat male reproductive system, primarily on the accessory organs and sperm within them at lower doses (31.25 and 62.5 mg/kg), and on the testis at the highest dose (125 mg/kg). /Sodium dichloroacetate/[Toth GP et al; Fundam Appl Toxicol 19 (1): 57-63 (1992)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: Maternal exposure to high doses of ... dichloroacetic acid (DCA), has been implicated in eye malformations in fetal rats, primarily micro-/anophthalmia. Subsequent to a cardiac teratology study of these compounds ... their potential to induce ocular malformations was examined in a subset of the same experimental animals. Pregnant, Sprague-Dawley Crl:CDR BR rats were orally treated on gestation days (GDs) 6 to 15 with bolus doses of ... DCA (300 mg/kg/day) or all-trans retinoic acid (RA; 15 mg/kg/day). The heads of GD 21 fetuses were not only examined grossly for external malformations, but were sectioned using a modified Wilson's technique and subjected to computerized morphometry that allowed for the quantification of lens area, globe area, medial canthus distance, and interocular distance. Gross ocular malformations were essentially absent in all treatment groups except for the RA group in which 26% of fetuses exhibited micro-/anophthalmia. Using the litter as the experimental unit of analysis, lens area, globe area, and interocular distance were statistically significantly reduced in the DCA treatment group. Statistically significant reductions in lens and globe areas also occurred in the RA treatment group ... Because DCA ... treatments were associated with significant reductions in fetal body weight (bw), data were also statistically analyzed after bw adjustment. Doing so dramatically altered the results of treatment group comparisons, but the severity of bw reduction and the degree of change in ocular measures did not always correlate. This suggests that bw reduction may not be an adequate explanation for all the changes observed in ocular measures. Thus, it is unclear whether DCA specifically disrupted ocular development even under these provocative exposure conditions...[Warren DA et al; Int J Toxicol 25 (4): 279-84 (2006)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: Preimplantation embryos up to the 8 cell stage of development use lactate and pyruvate but not glucose or Krebs cycle intermediates to support growth, development, and cleavage. The dominant effect of dichloroacetic acid (DCA) is the irreversible stimulation of pyruvate dehydrogenase (PDH) activity, thus accelerating the oxidative metabolism of pyruvate and lactate. To test the hypothesis that early induction of oxidative metabolism in 2 cell murine embryos accelerates preimplantation embryo cleavage rates, female B6C3Fl mice at 6 to 8 weeks of age were superovulated with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) and mated. All 2 cell stage embryos were randomly assigned to culture media with or without 130 ug/mL DCA. The developmental stage of all embryos was then noted every 24 hours for a total of 72 hours. Chi-square analysis and the method of average rank sum were used to compare the distribution of embryos at each observation point. At 24 hours, DCA-exposed embryos had achieved an advanced stage of growth and development relative to controls (average rank sum, P = 0.026; chi-square distribution, P = 0.047). Subsequently, at 48 and 72 hours, neither the average rank sum nor the chi-square distribution was different. /Results/ suggest that DCA accelerates early growth and development of murine embryos before implantation, possibly through the early induction of oxidative metabolism.[Penzias AS, et al; 42 (9):1077-80 (1993)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: The developmental effects of dichloroacetic acid (DCA) were evaluated in the pregnant Long-Evans rat. In two separate studies, animals were dosed by oral intubation on gestation days 6-15 (plug = 0) with 0, 900, 1,400, 1,900 or 2,400 mg/kg/day and 0, 14, 140, or 400 mg/kg/day. The vehicle control was distilled water. Maternal observations included clinical signs, weight change, and gross evaluation of organ weights and uterine contents at necropsy (day 20). Corpora lutea were counted and uteri stained for implantation sites. Live fetuses were examined for external, skeletal, and soft tissue malformations. Seven dams died during treatment (1,400 mg 1/19, 1,900 mg 2/19, 2,400 mg 4/21), and maternal weight gain was reduced at all except the lowest treatment levels. Liver, spleen, and kidney weights increased in a dose-related manner. The mean percentage of resorbed implants per litter was significantly elevated at greater than or equal to 900 mg/kg/day. Live fetuses showed dose-dependent reductions in weight and length at doses above 140 mg/kg. Statistically significant frequencies of soft tissue malformations ranged from 2.6% (140 mg/kg) to 73% (2,400 mg/kg). These were principally in the cardiovascular system and predominantly comprised defects between the ascending aorta and the right ventricle. Skeletal malformations were not observed in significant numbers in any dose group.[Smith MK et al; Teratology 46 (3): 217-23 (1992)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: The embryotoxicity of ... dichloroacetic acid ... was studied in vitro, using the rat whole embryo culture system. Embryos from Sprague-Dawley rats were explanted on gestational day 10 (plug day = day 0) and cultured for 46 hr in the presence of the test chemical. /Dichloroacetic acid/ ... produced concentration-dependent decreases in growth and differentiation and increases in the incidence of morphologically abnormal embryos...[Saillenfait AM et al; Arch Toxicol. 1995;70(2):71-82.] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: The objective of this study was to orally treat pregnant CDR(CD) Sprague-Dawley rats with large bolus doses of ... DCA (300 mg/kg) once per day on days 6 through 15 of gestation to determine the effectiveness of these materials to induce cardiac defects in the fetus. All-trans retinoic acid (RA) dissolved in soybean oil was used as a positive control. ... Water was used as the dosing vehicle ... Fetal hearts were examined on gestation day (GD) 21 by an initial in situ, cardiovascular stereomicroscope examination, and then followed by a microscopic dissection and examination of the formalin-fixed heart. The doses selected ... resulted in a modest decrease in maternal weight gain during gestation ... . The fetal weights on GD 21 ... were decreased ... 9% ... compared to the water control group and 21% in the RA treatment group compared to soybean oil control group. The heart malformation incidence for fetuses from the ... DCA-treated dams did not differ from control values on a per fetus or per litter basis. The rate of heart malformations, on a per fetus basis, ranged from 3% to 5% ... for treatment groups compared to 6.5% and 2.9% for soybean oil and water control groups. The RA treatment group was significantly higher with 33% of the fetuses displaying heart defects. For ... DCA treatment groups 42% to 60% of the litters contained at least one fetus with a heart malformation, compared to 52% and 37% of the litters in the soybean oil and water control groups. For the RA treatment group, 11 of 12 litters contained at least one fetus with a heart malformation...[Fisher JW et al; Int J Toxicol 20 (5): 257-67 (2001)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Developmental or Reproductive Toxicity: The testicular toxicity of dichloroacetic acid (DCA) ... drinking water, was evaluated in adult male rats given both single and multiple (up to 14 d) oral doses. Delayed spermiation and altered resorption of residual bodies were observed in rats given single doses of 1500 and 3000 mg/kg; these effects persisted to varying degrees on post-treatment days 2, 14, and 28. Delayed spermiation and formation of atypical residual bodies also were observed on days 2, 5, 9, and 14 in rats dosed daily with 1440, 480, 160, and 54 mg/kg. Distorted sperm heads and acrosomes were observed in step 15 spermatids after 14 doses of 480 and 1440 mg/kg. Decreases in the percentage of motile sperm occurred after 9 doses of 480 and 1440 mg/kg and 14 doses of 160 mg/kg. Increased numbers of fused epididymal sperm were observed on days 5, 9, and 14 in rats dosed with 1440, 480, and 160 mg/kg, respectively; other morphologic abnormalities occurred at 160 mg/kg and higher. On day 14, a significant decrease in epididymis weight was observed at 480 and 1440 mg/kg, and epididymal sperm count was decreased at 160 mg/kg and higher. These studies demonstrate that the testicular toxicity induced by DCA are similar to those produced by the analogue, dibromoacetic acid. However, the testicular toxicity of DCA is less severe at equal molar concentrations. Moreover, the DCA-induced testicular lesions occur with greater potency as the duration of dosing increases, indicating the importance of using low-dose subchronic exposures to assess the health risk of prevalent disinfection byproducts.[Linder RE et al; Reprod Toxicol 11 (5): 681-8 (1997)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Neurotoxicity: Dichloroacetic acid (DCA) is ... a known neurotoxicant in rats, dogs, and humans. ... DCA neurotoxicity in rats /was characterized/ using a neurobehavioral screening battery under varying exposure durations (acute, subchronic, and chronic) and routes of administration (oral gavage and drinking water). Studies were conducted in both weanling and adult rats, and comparisons were made between Long-Evans and Fischer-344 rats. DCA produced neuromuscular toxicity comprised of limb weakness and deficits in gait and righting reflex; altered gait and decreased hindlimb grip strength were the earliest indicators of toxicity. Other effects included mild tremors, ocular abnormalities, and a unique chest-clasping response (seen in Fischer-344 rats only). Neurotoxicity was permanent (i.e., through 2 years) following a 6-month exposure to high dose levels, whereas the effects of intermediate dose levels with exposures of 3 months or less were slowly reversible. The severity, specificity, and recovery of neurological changes were route, duration, and strain dependent. Fischer-344 rats were more sensitive than Long-Evans rats, and weanling rats may be somewhat more sensitive than adults. Oral gavage produced significantly less toxicity compared to the same intake level received in drinking water. Neurotoxicity was progressive with continued exposure, and was observed at exposure levels as low as 16 mg/kg/day (lowest dose level tested) when administered via drinking water in subchronic studies. The data from these studies characterize the neurotoxicity produced by DCA, and show it to be more pronounced, persistent, and occurring at lower exposures than has been previously reported...[Moser VC et al; Neurotoxicol Teratol 21 (6): 719-31 (1999)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Neurotoxicity: The chronic use of dichloroacetate (DCA) for diabetes mellitus or hyperlipoproteinemias has been compromised by neurologic and other forms of toxicity. ... For 7 weeks, rats were fed ad lib. Purina chow and water or chow plus sodium DCA (50 mg/kg or 1.1 g/kg) in water. A portion of the DCA-treated animals also received intraperitoneal injections of 600 ug thiamine three times weekly or 600 micrograms thiamine daily by mouth. Thiamine status was assessed by determining red cell transketolase activity and, in a blinded manner, by recording the development of clinical signs known to be associated with thiamine deficiency. At the 50 mg/kg dose, chronic administration of DCA showed no clinical toxicity or effect on transketolase activity. At the 1.1 g/kg dose, however, DCA markedly increased the frequency and severity of toxicity and decreased transketolase activity 25%, compared to controls. Coadministration of thiamine substantially reduced evidence of thiamine deficiency and normalized transketolase activity. Inhibition of transketolase by DCA in vivo was not due to a direct action on the enzyme, however, since DCA, glyoxylate, or oxalate had no appreciable effects on transketolase activity in vitro. After 7 weeks, plasma DCA concentrations were similar in rats receiving DCA alone or DCA plus thiamine, while urinary oxalate was 86% above control in DCA-treated rats but only 28% above control in DCA plus thiamine-treated animals. No light microscopic changes were seen in peripheral nerve, lens, testis, or kidney morphology in either DCA-treated group, nor was there disruption of normal sperm production in the DCA-treated group. /It was concluded/ that stimulation by DCA of thiamine-requiring enzymes may lead to depletion of total body thiamine stores and to both a fall in transketolase activity and an increase in oxalate accumulation in vivo. DCA neurotoxicity may thus be due, at least in part, to thiamine deficiency and may be preventable with thiamine treatment.[Stacpoole PW et al; Fundam Appl Toxicol 14 (2): 327-37 (1990)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: ...The objective of the present study was to examine the toxic effects of monochloroacetic acid (MCA), dichloroacetic acid (DCA), and trichloroacetic acid (TCA) in a 90-day subchronic study in rats via oral exposure by drinking water. Chloroacetic acid solutions were prepared at concentrations which provided an approximate intake of 1/4 the LD50 dose per day: MCA, 1.9 mM; DCA, 80.5 mM; TCA, 45.8 mM. Control rats received distilled water only. After 90 days, major organs were removed, fixed, paraffin embedded, and stained. Light microscopic examination of the major organs revealed variable degrees of alterations in the lung and liver of all three treated groups. In the liver, morphological changes were predominantly localized to the portal triads, which were mildly to moderately enlarged with random bile duct proliferation, extension of portal veins, fibrosis, edema, and occasional foci of inflammation. In the lungs, minimal alterations were observed as foci of perivascular inflammation on small pulmonary veins. Morphological changes in the testes and brain were seen only in the DCA treated group. Testes were atrophic with few spermatocytes and no mature spermatozoa. Focal vacuolation and gliosis were present in the forebrain and brainstem. The results of these studies indicate that, relative to their respective LD50 values, DCA given at 80.5 mM is more toxic than TCA given at 45.8 mM and MCA at 1.9 mM is least toxic.[Bhat HK et al; Fundam Appl Toxicol 17 (2): 240-53 (1991)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: Administration of dichloroacetate (DCA) in drinking water results in accumulation of glycogen in the liver of B6C3F1 mice. To investigate the processes affecting liver glycogen accumulation, male B6C3F1 mice were administered DCA in drinking water at levels varying from 0.1 to 3 g/L for up to 8 weeks. Liver glycogen synthase (GS) and glycogen phosphorylase (GP) activities, liver glycogen content, serum glucose and insulin levels were analyzed. To determine whether effects were primary or attributable to increased glycogen synthesis, some mice were fasted and administered a glucose challenge (20 min before sacrifice). DCA treatments in drinking water caused glycogen accumulation in a dose-dependent manner. The DCA treatment in drinking water suppressed the activity ratio of GS measured in mice sacrificed at 9:00 AM, but not at 3:00 AM. However, net glycogen synthesis after glucose challenge was increased with DCA treatments for 1-2 weeks duration, but the effect was no longer observed at 8 weeks. Degradation of glycogen by fasting decreased progressively as the treatment period was increased, and no longer occurred at 8 weeks. A shift of the liver glycogen-iodine spectrum from DCA-treated mice was observed relative to that of control mice, suggesting a change in the physical form of glycogen. These data suggest that DCA-induced glycogen accumulation at high doses is related to decreases in the degradation rate. When DCA was administered by single intraperitoneal (ip) injection to naïve mice at doses of 2-200 mg/kg at the time of glucose challenge, a biphasic response was observed. Doses of 10-25 mg/kg increased both plasma glucose and insulin concentrations. In contrast, very high ip doses of DCA (> 75 mg/kg) produced progressive decreases in serum glucose and glycogen deposition in the liver... /Dichloroacetate/[Kato-Weinstein J et al; Toxicology 130 (2-3): 141-54 (1998).] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: B6C3F1 mice and Sprague-Dawley rats were provided drinking water containing 6-31 mM (1-5 g/liter) trichloroacetic acid (TCA), 8-39 mM (1-5 g/liter) dichloroacetic acid (DCA), or 11-32 mM (1-3 g/liter) monochloroacetic acid (MCA) for 14 days. TCA and DCA, but not MCA, increased the mouse relative liver weight in a dose-dependent manner. Rat liver weights were not altered by TCA or DCA treatment, but were depressed by MCA. Hepatic peroxisome proliferation was demonstrated by (1) increased palmitoyl-CoA oxidase and carnitine acetyl transferase activities, (2) appearance of a peroxisome proliferation-associated protein, and (3) morphometric analysis of electron micrographs. Mouse peroxisome proliferation was enhanced in a dose-dependent manner by both TCA and DCA, but only the high DCA concentration (39 mM) increased rat liver peroxisome proliferation. MCA was ineffective in both species. Three other mouse strains (Swiss-Webster, C3H, and C57BL/6) and two strains of rat (F344 and Osborne-Mendel) were examined for sensitivity to TCA. TCA (12 and 31 mM) effectively enhanced peroxisome proliferation in all mouse strains, especially the C57BL/6. A more modest enhancement in the Osborne-Mendel (288%) and F344 rat (167%) was seen. Dosing F344 rats with 200 mg/kg TCA in water or corn oil for 10 days increased peroxisome proliferation 179 and 278%, respectively, above the vehicle controls. These studies demonstrate that the mouse is more sensitive than the rat with respect to the enhancement of liver peroxisome proliferation by TCA and DCA and suggest that if peroxisome proliferation is critical for the induction of hepatic cancer by TCA and DCA, then the rat should be less sensitive or refractory to tumor induction.[DeAngelo AB et al; Toxicol Appl Pharmacol 101 (2): 285-98 (1989)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: Exposure of male and female Sprague-Dawley rats to dichloroacetic acid at target doses of 10-600 mg/kg body weight per day in the drinking water for 14 days resulted in reduced weight gain only in the group given the highest dose. Treatment also increased urinary excretion of ammonia and changed the activities of enzymes of ammoniagenesis, indicating renal compensation for an acid load.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 281 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: Induction of peroxisome proliferation has been repeatedly associated with the chronic toxicity and carcinogenicity of dichloroacetic acid to the liver. It can induce peroxisome proliferation in the livers of both mice and rats, as indicated by increased activities of palmitoyl coenzyme A oxidase and carnitine acetyl transferase, the appearance of a peroxisome proliferation associated protein and increased volume-density of peroxisomes after exposure to dichloroacetic acid for 14 days.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 282 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: Male Sprague Dawley rats administered dichloroacetic acid in the drinking water for 90 days at concentrations providing daily doses of about 4, 35 or 350 mg/kg body weight had decreased body weights. Animals given the high dose also showed histological and biochemical signs of liver and kidney damage and increased hepatic peroxisomal beta-oxidation activity.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 281 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: Male Sprague Dawley rats were given dichloroacetic acid in the drinking water at a concentration of 80.5 mmol/L (10 g/L) to provide an approximate intake of 1100 mg/kg body weight per day. After 90 days, body weights were decreased, and there was an 11% increase in liver weight and a 34% decrease in testicular weight; histopathological changes were seen in the liver and lung.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 281 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: Male Sprague-Dawley rats were treated with ... dichloroacetic acid (DCA) ... in the drinking water at levels of 0, 50, 500 and 5000 ppm for a period of 90 days to determine the toxicities associated with subchronic exposure. All animals were sacrificed and examined for gross and histopathologic lesions, serochemical changes, immune dysfunction, hepatic peroxisomal and mixed function oxidase enzyme induction and organ-body weight changes. Animals treated with DCA had decreased body weight gains (500 and 5000 ppm) and decreased total serum protein (all doses) ... /and/ increased liver and kidney organ to body weight /(500 or 5000 ppm)/ ratios. Rats offered DCA had significantly elevated alkaline phosphatase (500 and 5000 ppm) and alanine-amino transferase (5000 ppm). No consistent immunotoxicity was observed in animals exposed to either compound. Rats treated with 5000 ppm trichloroacetic acid or dichloroacetic acid had significantly increased hepatic peroxisomal beta-oxidation activity.[Mather GG et al; Toxicology 64 (1): 71-80 (1990)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: Male and female juvenile beagle dogs were dosed daily for 90 days with dichloroacetate (DCA). The compound was administered orally via gelatin capsules at doses of 0, 12.5, 39.5, and 72 mg/kg/day. Each dose group consisted of five males and five females. The dogs were observed clinically and blood samples were taken at 15-day intervals for hematologic and serum chemistry values. Decreased total erythrocyte count and hemoglobin levels were observed in mid- and high-dose dogs beginning at Day 30. Serum concentrations of LDH were elevated at Days 30 and 45 in females and at Day 75 in males treated with DCA at 72 mg/kg/day. One female of the high-dose group died at Day 50 and two high-dose males died at Days 51 and 74. Hindlimb partial paralysis was observed in many high-dose dogs. Vacuolization of myelinated white tracts of cerebrum, cerebellum, and/or spinal cord was observed in many high-dose dogs as well as some mid- and low-dose subjects. Degeneration of testicular germinal epithelium and syncytial giant cell formation was noted in males of all dose groups. Hepatic vacuolar change and chronic hepatitis appeared only in DCA-treated dogs. In addition, suppurative bronchopneumonia and chronic pancreatitis were noted in many high-dose and some middose subjects. A "no-adverse-effect level" was not determined in this study. /Dichloroacetate/[Cicmanec JL et al; Fundam Appl Toxicol 17 (2): 376-89 (1991)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: Mice were treated with dichloroacetic acid (DCA) and trichloroacetic acid (TCA) for 10 days and their livers examined for evidence of peroxisome proliferation. An increase in liver weight was observed, particularly with DCA. Both TCA and DCA increased peroxisomal beta-oxidation in liver homogenates, with TCA-treated animals showing more activity than those treated with DCA. Electron microscopy revealed that the number of peroxisomes were approximately the same in DCA- and TCA-treated animals. However, peroxisomes induced by DCA treatment frequently lacked nucleoid cores. These data indicate that peroxisomes induced by these compounds differ in their concentration of peroxisomal enzymes. Except for a slight hypertrophy, repeated doses of TCA do not produce significant degenerative changes in the liver of mice. Repeated doses of DCA produce multifocal, subcapsular necrotic regions, and a marked hypertrophic response in the liver. Mice treated with TCA for 10 days and sacrificed 24 hr after the last dose did not display increased strand breaks in hepatic DNA...[Nelson MA et al; Toxicology 58 (3): 239-48 (1989)] **PEER REVIEWED** PubMed Abstract
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: Ocular toxicity was observed in beagle dogs (which are susceptible to drug induced cataract formation) that were treated for 13 weeks with an approximate dose of 1100 mg/kg body weight dichloroacetic acid in the drinking water. No similar organ specific effect has been seen in other studies or in other species.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 281 (1995)] **PEER REVIEWED**
  • LABORATORY ANIMALS: Subchronic or Prechronic Exposure: The effects of dichloroacetate (DCA) ... administered in drinking water /for 14 days/ were studied. /The concentration of DCA used (0, 0.03, 0.125, 0.5, and 1.875 g/L) were chosen to yield target doses of (0, 10, 40, 150, and 600 mg/kg/day)/. At high concentrations ... weight loss, or failure to gain weight, was observed. Food consumption was also decreased; both effects were attributed to decreased water consumption. Renal phosphate-dependent glutaminase activity was increased at the highest concentration, and urinary ammonia was also increased. These changes indicated renal adaptation to an acid load. DCA, in pharmacological doses, impairs gluconeogenesis from lactate in part by decreasing lactate availability. Similar tendencies were observed in the present studies; however, female rats showed a biphasic response. At lower DCA concentrations, tissue lactate and plasma glucose concentrations were increased, whereas at higher concentrations of DCA, the expected decreases were observed. /Dichloroacetate/[Davis ME; Environ Health Perspect 69: 209-14 (1986)] **PEER REVIEWED** PubMed Abstract Full text: PMC1474340
  • OTHER TOXICITY INFORMATION: ... 6-week-old medaka were exposed to diethylnitrosamine (DEN, a known initiator), followed by continuous exposure to 0.5 or 2.0 g/L dichloroacetic acid (DCA) in the ambient water, over a 4 week period. At both exposure concentrations, changes in the liver included marked hepatocellular cytoplasmic vacuolation, cytomegaly, karyomegaly, nuclear atypia and multifocal areas of hepatocellular necrosis and loss as early as week two of DCA exposure. The majority of the hepatocellular cytoplasmic vacuoles were shown by periodic acid Schiff (PAS) staining to contain large amounts of glycogen. These elevated glycogen levels may reflect a disruption in the enzyme pathways for glycolysis. The total cellular changes seen in this short-term exposure regimen are compatible with preneoplastic changes seen in rats and mice exposed to DCA...[McHugh Law J et al; Toxicol Lett 94 (1): 19-27 (1998)] **PEER REVIEWED** PubMed Abstract
  • OTHER TOXICITY INFORMATION: ... Dichloroacetate (DCA) treatment in rodents ameliorates, via activation of the pyruvate dehydrogenase complex, the cardiovascular depression observed after hemorrhagic shock. To explore the mechanism of this effect, we administered DCA in a large animal model of hemorrhagic shock. Mongrel hounds were anesthetized with 1.5% isoflurane and were measured for hemodynamics, myocardial contractility, and myocardial substrate utilization. They were hemorrhaged to a mean arterial pressure of 35 mm Hg for 90 min or until arterial lactate levels reached 7.0 mM (1137 +/- 47 mL or 49 +/- 2% total blood volume). Animals were chosen at random to receive DCA dissolved in water or an equal volume of saline at the onset of resuscitation. Two-thirds of the shed blood volume was returned immediately after giving an equivalent volume of saline. Two hours after the onset of resuscitation, mean arterial pressure was not different between DCA and control groups (79 +/- 3 vs. 82 +/- 3 mm Hg, respectively). Arterial lactate levels were significantly reduced by DCA (0.5 +/- 0.06 vs. 2.0 +/- 0.2 mM). However, DCA treatment was associated with a decreased stroke volume index (0.56 +/- 0.06 vs. 0.82 +/- 0.08 mL/kg/beat) and a decreased myocardial efficiency (19 vs. 41 L x mm Hg/mL/100 g tissue). During resuscitation by DCA, myocardial lactate consumption was reduced (21.4 +/- 3.7 vs. 70.7 +/- 16.3 umole/min/100 g tissue) despite a three-fold increase in myocardial pyruvate dehydrogenase activity, while free fatty acid levels actually began to rise. Although increased lactate oxidation should be beneficial during resuscitation, /it was proposed/ that DCA treatment led to a deprivation of myocardial lactate supply, which reduced net myocardial lactate oxidation, thus compromising myocardial function during resuscitation from hemorrhagic shock. /Dichloroacetate/[Barbee RW et al; Shock 14 (2): 208-14 (2000)] **PEER REVIEWED** PubMed Abstract
  • OTHER TOXICITY INFORMATION: ... The ability of dichloroacetic acid to elicit a lipid peroxidative response in liver was ... investigated in male Fischer 344 rats and male B6C3F1 mice after administration of a single oral dose of 100-2000 mg/kg body weight in water. A dose dependent response was induced up to 300 mg/kg body weight dichloroacetic acid in both species. A further increase to 1000 mg/kg body weight resulted in only minimal increases in the lipid peroxidative response in mice and in a decreased response in rats.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 278 (1995)] **PEER REVIEWED**
  • OTHER TOXICITY INFORMATION: ... This article ... presents a review of recently published scientific literature examining the effects of trichloroethylene (TCE) metabolites in the context of the /mode of action (MOA) of trichloroethylene carcinogenesis/ ... Studies of the TCE metabolites dichloroacetic acid (DCA), trichloroacetic acid (TCA), and chloral hydrate suggest that both DCA and TCA are involved in TCE-induced liver tumorigenesis and that many DCA effects are consistent with conditions that increase the risk of liver cancer in humans. Studies of S-(1,2-dichlorovinyl)-l-cysteine have revealed a number of different possible cell signaling effects that may be related to kidney tumorigenesis at lower concentrations than those leading to cytotoxicity. Recent studies of trichloroethanol exploring an alternative hypothesis for kidney tumorigenesis have failed to establish the formation of formate as a key event for TCE-induced kidney tumors. Overall, although MOAs and key events for TCE-induced liver and kidney tumors have yet to be definitively established, these results support the likelihood that toxicity is due to multiple metabolites through several MOAs, none of which appear to be irrelevant to humans.[Caldwell JC, Keshava N; Environ Health Perspect; 114 (9): 1457-63 (2006)] **PEER REVIEWED** PubMed Abstract Full text: PMC1570066
  • OTHER TOXICITY INFORMATION: ... Toxicokinetic studies have established that elimination of dichloroacetate (DCA) is controlled by liver metabolism, which occurs by the cytosolic enzyme glutathione-S-transferase-zeta (GST-zeta). DCA is also a mechanism based inhibitor of GST-zeta, and a loss in GST-zeta enzyme activity occurs following repeated doses or prolonged drinking water exposures. GST-zeta is identical to an enzyme that is part of the tyrosine catabolism pathway known as maleylacetoacetate isomerase (MAAI). ... The elimination of iv doses of DCA to young (10 week) and aged (60 week) mice previously treated with DCA in their drinking water for 2 and 56 weeks, respectively, /was studied/. The diurnal change in blood concentrations of DCA was also monitored in mice exposed to three different drinking water concentrations of DCA (2.0, 0.5 and 0.05 g/L). Additional experiments measured the in vitro metabolism of DCA in liver homogenates prepared from treated mice given various recovery times following treatment. The MAAI activity was also measured in liver cytosol obtained from treated mice. Results indicated young mice were the most sensitive to changes in DCA elimination after drinking water treatment. The in vitro metabolism of DCA was decreased at all treatment rates. Partial restoration (approximately 65% of controls) of DCA elimination capacity and hepatic GST-zeta activity occurred after 48 hr recovery from 14 d 2.0 g/LDCA drinking water treatments. Recovery from treatments could be blocked by interruption of protein synthesis with actinomycin D. MAAI activity was reduced over 80% in liver cytosol from 10-week-old mice. However, MAAI was unaffected in 60-week-old mice. These results indicate that in young mice, inactivation and re-synthesis of GST-zeta is a highly dynamic process and that exogenous factors that deplete or reduce GST-zeta levels will decrease DCA elimination and may increase the carcinogenic potency of DCA. As mice age, the elimination capacity for DCA is less affected by reduced liver metabolism and mice appear to develop some toxicokinetic adaptation(s) to allow elimination of DCA at rates comparable to naive animals. Reduced MAAI activity alone is unlikely to be the carcinogenic mode of action for DCA and may in fact, only be important during the early stages of DCA exposure. /Dichloroacetate/[Schultz IR et al; Toxicology 173 (3): 229-47 (2002); Erratum in: Toxicology 197 (3): 263-4 (2004)] **PEER REVIEWED** PubMed Abstract
  • OTHER TOXICITY INFORMATION: It is important to note that the dog appears to be very sensitive to the effects of dichloroacetic acid (DCA) on the liver; substantial increases in liver weights are observed at daily doses as low as 12.5 mg/kg of body weight per day for a 90-day period. By comparison, the lowest effect level noted in mice is 0.5 g/L of drinking-water, which approximates 70-100 mg/kg of body weight per day, and the lowest effect level noted in rats is 125 mg/kg of body weight per day.[Environmental Health Criteria 216: Disinfectants and DIsinfectant By-Products (1999) by the International Programme on Chemical Safety (IPCS) under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation and the World Health Organization. Available from, as of August 1, 2008: http://www.inchem.org/documents/ehc/ehc/ehc216.htm] **PEER REVIEWED**
  • OTHER TOXICITY INFORMATION: Spontaneous apoptosis in hepatocytes of male B6C3F1 mice that received dichloroacetic acid (DCA) in their drinking water for 5-30 days (28-58 days of life) was examined as part of ongoing studies to determine the molecular basis of the hepatocarcinogenicity of this nongenotoxic water chlorination by-product. DCA at 0.5 and 5.0 g/liter, significantly reduced apoptosis relative to untreated controls in a dose dependent fashion. Regression analysis indicated that apoptosis declined over the 30-day period in the livers of control, age paired animals receiving no drug. Animals receiving low dose DCA exhibited a similar, although quantitatively depressed, trend line, whereas animals receiving high-dose DCA showed maximal depression of apoptosis at 5 days, which was sustained throughout the course of the 30 day period. These studies suggest that DCA has the ability to down regulate apoptosis in murine liver. When taken together with previous data demonstrating DCA dependent decrease in labeling index in these same livers, these data further support the hypothesis that the carcinogenic mechanism of DCA may involve suppression of the ability of the liver to remove initiated cells by apoptosis rather than by induction of selective proliferation of initiated cells.[Snyder RD, et al; Cancer Res 55 (17): 3702-5 (1995)] **PEER REVIEWED** PubMed Abstract
  • Before beginning discussions of available toxicological evaluations of dichloroacetic acid (DCA), it is important to point out that this compound exists in drinking-water as the salt, despite the fact that it is widely referred to as dichloroacetic acid. DCA has a pKa of 1.48 at 25 deg C. As a consequence, it occurs almost exclusively in the ionized form at the pHs found in drinking-water (broadly speaking, a pH range of 5-10). Failure to recognize this has resulted in a number of studies that have employed the free acid in test systems. At low doses, the buffering capacity of the physiological system can neutralize acid, and the measured activity may in fact be representative. However, most of the experimentation has been conducted using doses ranging from 50 to 1000 mg/kg of body weight in vivo or in the mmol/liter range in vitro. Therefore, the applicability of the results of such studies to estimating human risks will be uncertain because of the large pH artefacts that can be expected when administering these quantities of a strong acid.[Environmental Health Criteria 216: Disinfectants and Disinfectant By-Products (1999) by the International Programme on Chemical Safety (IPCS) under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation and the World Health Organization. Available from, as of August 1, 2008: http://www.inchem.org/documents/ehc/ehc/ehc216.htm] **PEER REVIEWED**

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Human Toxicity Values

  • None found

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Non-Human Toxicity Values

  • None found

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Absorption, Distribution And Excretion

  • ... Biotransformation of dichloroacetic acid (DCA) by glutathione transferase zeta (GSTzeta) in the liver is the major elimination pathway in humans. GSTzeta is also inactivated by DCA, leading to slower systemic clearance and nonlinear pharmacokinetics after multiple doses. A physiologically based pharmacokinetic (PBPK) model was developed to quantitatively describe DCA biotransformation and kinetics in humans administered DCA by intravenous infusion and oral ingestion. GSTzeta metabolism was described using a Michaelis-Menten equation coupled with rate constants to account for normal GSTzeta synthesis, degradation and irreversible covalent binding and inhibition by the glutathione-bound-DCA intermediate. With some departures between observation and model prediction, the human DCA PBPK model adequately predicted the DCA plasma kinetics over a 20,000-fold range in administered doses. Apparent inhibition of GSTzeta mediated metabolism of DCA was minimal for low doses of DCA (ug/kg day), but was significant for therapeutic doses of DCA. Plasma protein binding of DCA was assumed to be an important factor influencing the kinetics of low doses of DCA (ug/kg day). Polymorphisms of GSTzeta may help explain inter-individual variability in DCA plasma kinetics and warrants evaluation...[Li T et al; Toxicology 245 (1-2): 35-48 (2008); Erratum in: Toxicology 247 (2-3): 166 (2008)] **PEER REVIEWED** PubMed Abstract
  • ... Seven subjects with cirrhosis and six healthy volunteers received a 5-hour primed constant infusion of 6,6-2H2-glucose. After a 2-hour basal period, subjects received intravenous dichloroacetate, 35 mg/kg, over 30 minutes. Dichloroacetate pharmacokinetics were compared by the mixed-effects population-based technique. Glucose production was calculated by means of isotope dilution. ... Peak plasma dichloroacetate concentration in subjects with cirrhosis did not differ from that in control subjects, but typical dichloroacetate clearance was only 36% of that in control subjects (P <0 .001). Dichloroacetate decreased plasma lactate concentration by approximately 50% (P < 0.001), glucose production by 7% to 9% (P < 0.05), and plasma glucose concentration by 9% to 14% (P < 0.05) in both subjects with cirrhosis and control subjects. Dichloroacetate-induced decreases in plasma lactate and glucose concentrations and in glucose production in subjects with cirrhosis did not differ from those in control subjects. ... Plasma dichloroacetate clearance is markedly decreased in patients with cirrhosis, likely because of compromised hepatic function. Subjects with cirrhosis exhibit neither exaggerated inhibition of glucose production nor increased risk of hypoglycemia as a result of acute dichloroacetate-induced hypolactatemia. /Dichloroacetate/[Shangraw RE, Fisher DM; Clin Pharmacol Ther 66 (4): 380-90 (1999)] **PEER REVIEWED** PubMed Abstract
  • ... The kinetics and biotransformation of dichloroacetate (DCA) and its effects on tyrosine metabolism /were measured/ in nine patients treated for 6 months with 25 mg/kg/day and in rats treated for 5 days with 50 mg/kg/day. ... The activity and expression of hepatic GSTz1/MAAI /was also measured/. Chronic administration of DCA causes a striking age-dependent decrease in its plasma clearance and an increase in its plasma half-life in patients and rats. Urinary excretion of unchanged DCA in rats increases with age, whereas oxalate, an end product of DCA metabolism, shows the opposite trend. Low concentrations of monochloroacetate (MCA), which is known to be neurotoxic, increase as a function of age in the urine of dosed rats. MCA was detectable in plasma only of older animals. Hepatic GSTz1/MAAI-specific activity was inhibited equally by DCA treatment among all age groups, whereas plasma and urinary levels of maleylacetone, a natural substrate for this enzyme, increased with age. We conclude that age is an important variable in the in vivo metabolism and elimination of DCA and that it may account, in part, for the neurotoxicity of this compound in humans and other species. /Dichloroacetate/[Shroads AL et al; J Pharmacol Exp Ther 324 (3): 1163-71 (2008)] **PEER REVIEWED** PubMed Abstract Full text: PMC2613565
  • ... The pharmacokinetics, pharmacodynamics and toxicity of dichloroacetate (DCA) were evaluated in 11 patients with severe malaria, and their lactate responses compared with nine control patients in an open-label prospective study. Intravenous DCA (46 mg/kg infused in 30 min) or saline placebo was given on admission to the study, and 12 hr later, as an adjunct to standard quinine treatment. An open one-compartment model with the following parameters described the pharmacokinetics of DCA after one dose (mean (s.d.)): V = 0.44(0.2) L/kg; CL = 0.13 [0.027] L/h/kg; Cmax = 106(28) mg/L; t1/2 = 3.4(2.2) hr. After two doses of DCA (n = 9) the pharmacokinetic parameters were similar to those after the first dose. DCA decreased venous plasma lactate concentrations by 42% of baseline values 8 h after admission, normalized arterial pH from a mean(s.d.) of 7.367(0.063) to 7.39(0.1), and decreased the calculated base deficit from 9.2(7.3) mEq/L to 6.4(10.4) mEq/L. In control patients lactate concentrations fell by approximately 14% of baseline concentrations (P < 0.02 compared with DCA recipients). Venous lactate concentrations fell a further 16% from baseline values after the second dose of DCA but this change was not significantly different from controls. There was no electrocardiographic or other evidence of toxicity associated with DCA...[Krishna S et al; Br J Clin Pharmacol 41 (1): 29-34 (1996)] **PEER REVIEWED** PubMed Abstract
  • ...The amount of dichloroacetic acid excreted by humans after having swum in a chlorinated pool /was measured/, and this ranged from 25 to 960 ng per one urine void. The background excretion rate varied from 109 to 253 ng per one urine void. ...An average excretion rate of 1.04 ng/min dichloroacetic acid /was measured/ in subjects exposed to low levels (1.76 ug/L) and 1.47 ng/min dichloroacetic acid in subjects exposed to high levels (32.7 ug/L) of dichloroacetic acid in water.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 362 (2004)] **PEER REVIEWED**
  • Dichloroacetate (DCA) ... 1,2-(13)C-DCA /in environmentally relevant concentrations was/ administered to healthy adults. Subjects received an oral or intravenous dose of 2.5 ug/kg of 1,2-(13)C-DCA. ... Plasma concentrations of 1,2-(13)C-DCA peaked 10 minutes and 30 minutes after intravenous or oral administration, respectively. Plasma kinetic parameters varied as a function of dose and duration. Very little unchanged 1,2-(13)C-DCA was excreted in urine. Trace amounts of DCA alter its own kinetics after short-term exposure. These findings have important implications for interpreting the impact of this xenobiotic on human health. /Dichloroacetate/[Jia M et al; J Clin Pharmacol 46 (12): 1449-59 (2006)] **PEER REVIEWED** PubMed Abstract
  • Dichloroacetic acid was given intravenously (50 mg/kg bw) or orally (50 mg/kg bw or 50 mg/kg bw plus 50 mg thiamine (vitamin B1) to healthy human volunteers (eight men and four women, aged 18 to 45 years), and a range of pharmacokinetic parameters were measured (Curry et al., 1991). On average, there was no evidence of an effect of vitamin B1 on the kinetics of dichloroacetic acetic. The average plasma half-life was 2.7 +/- 0.4 hr, the average volume of distribution was 19.9 +/- 1.7 L, the average area-under-the-curve (AUC) was 608.9 +/- 61.0 ug/hr/mL and the average renal clearance was 53.0 +/- 15.9 mL/hr. There was no difference in the AUC or elimination half-life between men and women. Only 0.7 +/- 0.5% dichloroacetic acid was excreted unchanged in the urine. Urinary excretion of oxalic acid was similar after oral or intravenous administration of dichloroacetic acid (2.1 +/- 0.8 mg versus 2.3 +/- 0.5 mg). However, the elimination half-life was markedly prolonged after a second dose of dichloroacetic acid.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 370 (2004)] **PEER REVIEWED**
  • Pharmacokinetic studies with dichloroacetate (DCA) provide insights into the likelihood that trichloroethylene-induced liver cancers arise from formation of DCA as a metabolite ... A simple physiologically based pharmacokinetic model was developed to analyze DCA blood concentration data from mice unexposed to or pre-treated with DCA. The large first pass metabolism of DCA in the liver is significantly reduced by DCA pretreatment. Because DCA inhibits its own metabolism, large increases in area under the blood concentration curve occur at lower doses than would be predicted from single-dose pharmacokinetic studies with naive mice. The dose metrics associated with the incidence of liver tumors in contrast to the multiplicity of tumors per animal may be different, suggesting potentially different roles in the cancer process for DCA versus its metabolites. By linking a model for trichloroethylene (TCE) pharmacokinetics with the DCA model, maximum levels of DCA potentially produced from TCE were estimated to be at or below the analytical chemistry detection limits. In addition, the predicted levels of DCA would be too small to produce the observed liver cancers following corn oil gavage exposure of mice to TCE.[Barton HA et al; Toxicol Lett 106 (1): 9-21 (1999)] **PEER REVIEWED** PubMed Abstract
  • The disposition of dichloroacetic acid (10 or 20 mg/kg bw given intravenously) was studied in four human volunteers (26, 38, 42 and 52 years old (sex not stated)). In subjects given 10 mg/kg bw dichloroacetic acid, the average plasma half-life was 0.34 hr (range, 0.33 - 0.36 hr), the average volume-of-distribution was 337 mL/kg (range, 308 - 366 mL/kg) and the average plasma clearance was 11.31 mL/min/kg (range, 10.86 - 11.76 mL/min/kg); in subjects given 20 mg/kg bw dichloroacetic acid, the average plasma half-life was 0.51 hr (range, 0.41-0.61 hr), the average volume-of-distribution was 190 mL/kg (range, 186 - 195 mL/kg) and the average plasma clearance was 4.55 mL/min/kg (range, 3.53 - 5.58 mL/min/kg).[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 369 (2004)] **PEER REVIEWED**
  • The disposition of dichloroacetic acid (DCA) was investigated in Fischer 344 rats over the 48 hr after oral gavage of 282 mg/kg of 1- or 2-(14C)-DCA (1-DCA or 2-DCA) and 28.2 mg/kg of 2-DCA. DCA was absorbed quickly, and the major route of disposition was through exhalation of carbon dioxide and elimination in the urine. The dispositions of 1- and 2-DCA at 282 mg/kg were similar. With 2-DCA, the disposition differed with dose in that the percentage of the dose expired as carbon dioxide decreased from 34.4% (28.2 mg/kg) to 25.0% (282 mg/kg), while the percentage of the radioactivity excreted in the urine increased from 12.7 to 35.2%. This percentage increase in the urinary excretion was mostly attributable to the presence of unmetabolized DCA, which comprised more than 20% at the higher dose and less than 1% at the lower dose. The major urinary metabolites were glycolic acid, glyoxylic acid, and oxalic acid. DCA and its metabolites accumulated in the tissues and were eliminated slowly. After 48 hr, 36.4%, 26.2%, and 20.8% of the dose was retained in the tissues of rats administered 28.2 and 282 mg/kg of 2-DCA and 282 mg/kg of 1-DCA, respectively. Of the organs examined, the liver (4.9-7.9% of dose) and muscle (4.5-9.9%) contained the most radioactivity, followed by skin (3.3-4.5%), blood (1.4-2.6%), and intestines (1.0-1.7%)...[Lin EL et al; J Toxicol Environ Health 38 (1): 19-32 (1993)] **PEER REVIEWED** PubMed Abstract
  • The pharmacokinetics of dichloroacetic acid has been studied in humans with a range of diseases. In children (four boys and four girls, aged 1.5-10 years) with lactic acidosis due to severe malaria, dichloroacetic acid given intravenously at a dose of 50 mg/kg bw showed an average plasma half-life of 1.8 +/- 0.4 hr, a volume of distribution of 0.32 +/- 0.09 L/kg and an average AUC of 378 +/- 65 mg/L/hr[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 370 (2004)] **PEER REVIEWED**
  • The pharmacokinetics of dichloroacetic acid was compared in healthy volunteers (27 subjects) and in patients with traumatic brain injury (25 subjects; average age, 52.8 +/- 18.1 years). The healthy volunteers were given cumulative intravenous doses (two doses 8 hr apart) of 45, 90 or 150 mg/kg bw dichloroacetic acid; 16 patients with acute traumatic brain injury were given 60, 100 or 200 mg/kg bw dichloroacetic acid as a single intravenous dose; six other patients were given three intravenous doses (dose not stated) of dichloroacetic acid at 24-hr intervals; and three patients were given six intravenous doses (dose not stated) at 12-hr intervals. The initial clearance of dichloroacetic acid (4.82 L/hr) declined (1.07 L/hr) after repeated doses in patients with traumatic brain injury. Although the authors suggested several mechanisms by which the clearance of dichloroacetic acid might be decreased after repeated doses, they proposed that the enzyme responsible for the metabolism of dichloroacetic acid might be destroyed after repeated treatment with the compound.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 371 (2004)] **PEER REVIEWED**
  • The pharmacokinetics of dichloroacetic acid was studied in 111 patients (66 men, 56.0 +/- 18.4 years old) with lactic acidosis, who received dichloroacetic acid (50 mg/kg bw) by intravenous perfusion over 30 min, then a second perfusion of 50 mg/kg bw 2 hr after the beginning of the first. The pharmacokinetics was complex in the acutely ill patients studied and differed markedly from those observed in healthy volunteers. In healthy volunteers, the pharmacokinetics fitted a one-compartment model, whereas in the patients the data fitted one-, two- and three-compartment models. In the two-compartment model, the plasma half-life and plasma clearance were 18.15 +/- 3.12 hr (mean +/- standard error (SE)) and 0.041 L/kg/hr, respectively, after the first treatment, whereas the two values were 68.30 +/- 14.50 hr (mean +/- SE) and 0.017 L/kg/hr, respectively, after the second treatment. Plasma clearance of dichloroacetic acid tended to decrease as either the number of compartments or the number of treatments increased. The prolonged half-life and decreased plasma clearance indicate that repeated administration of dichloroacetic acid impairs its metabolism[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. 371 (2004)] **PEER REVIEWED**
  • The pharmacokinetics of dichloroacetic acid was studied in rats and dogs. Three male Sprague-Dawley rats and two male beagle dogs were given 100 mg/kg bw dichloroacetic acid intravenously; the average plasma elimination half-life was 2.97 hr (range, 2.1-4.4 hr) in rats and 20.8 hr (range, 17.1-24.6 hr) in dogs; the average volume of distribution was 932 mL/kg (range, 701-1080 mL/kg) in rats and 256 mL/kg (range, 249-262 mL/kg) in dogs; and the average plasma clearance was 4.22 mL/min/kg (range, 1.84-5.94 mL/min/kg) in rats and 0.146 mL/min/kg (range, 0.123-0.168 mL/min/kg) in dogs.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 371 (2004)] **PEER REVIEWED**
  • The toxicokinetics of dichloroacetic acid were investigated in male Fischer 344 rats during 48 hour after oral administration of 28.2 or 282 mg/kg body weight (14)C dichloroacetic acid. The percentage of radiolabel excreted in the urine increased from 12.7% at the lower dose to 35.2% at the high dose. Unmetabolized dichloroacetic acid comprised > 20% of the urinary radiolabel at the high dose and < 1% at the low dose. The percentage of the dose excreted as carbon dioxide decreased from 34.4% at the lower dose to 25% at the higher. Significant percentages of the administered dose were retained in the liver (4.9%-7.9%), muscle (4.5-9.9%), skin (3.3-4.5%) and intestines (1.0-1.7%).[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 278 (1995)] **PEER REVIEWED**

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Metabolism/Metabolites

  • ... Dichloroacetic acid (DCA) has been shown to inhibit its own metabolism by irreversibly inactivating glutathione transferase zeta (GSTzeta)...[Keys DA et al; Toxicol Sci 82 (2): 381-93 (2004)] **PEER REVIEWED** PubMed Abstract
  • ... This study focuses on the effect of prior administration of dichloroacetate (DCA) ... in drinking water on the pharmacokinetics of a subsequent challenge dose of DCA ... in male B6C3F1 mice. Mice were provided with DCA ... in their drinking water at 2 g/L for 14 days and then challenged with a 100 mg/kg iv (non-labeled) or gavage (14C-labeled) dose of DCA ... The challenge dose was administered after 16 hr fasting and removal of the haloacetate pre-treatment. The haloacetate blood concentration-time profile and the disposition of 14C were characterized and compared with controls. The effect of pre-treatment on the in vitro metabolism of DCA in hepatic S9 was also evaluated. Pre-treatment with DCA caused a significant increase in the blood concentration-time profiles of the challenge dose of DCA. No effect on the blood concentration-time profile of DCA was observed after pre-treatment with trichloroacetate (TCA). Pre-treatment with TCA had no effect on subsequent doses of DCA. Pre-treatment with DCA did not have a significant effect on the formation of 14CO2 from radiolabeled DCA. In vitro experiments with liver S9 from DCA-pre-treated mice demonstrated that DCA inhibits it own metabolism. These results indicate that DCA metabolism in mice is also susceptible to inhibition by prior treatment with DCA, however the impact on clearance is less marked in mice than in F344 rats ... /Dichloroacetate/[Gonzalez-Leon A et al; Chem Biol Interact 123 (3): 239-53 (1999)] **PEER REVIEWED** PubMed Abstract
  • ... This study was designed to characterize the kinetics of chloral hydrate (CH) metabolism, and the formation and elimination of trichloroacetate (TCA), dichloroacetate (DCA), trichloroethanol (TCOH), and trichloroethanol glucuronide (TCOG) in male B6C3F1 mice. Mice were dosed with 67.8, 678, and 2034 umol/kg of CH through the tail vein. At selected time points, mice were killed, and blood and liver samples were collected ... TCOH, TCOG, TCA, and DCA were detected over the study period. Formation and metabolism of CH metabolites seemed to be dose-dependent. The terminal half-lives of TCOH and TCOG were similar, ranging from 0.2 to 0.7 hr. TCA and DCA were formed rapidly from the metabolism of CH and cleared slowly from systemic circulation. The area under the blood concentration-time curve for DCA was 10-20% of that for TCA. Both TCA and DCA were slowly eliminated from systemic circulation. The concentration-time profile of DCA seemed to be driven by the blood concentration of TCA, suggesting the possibility of DCA formation from TCA metabolism.[Abbas RR et al; Drug Metab Dispos 24 (12): 1340-6 (1996); Erratum in: Drug Metab Dispos 25 (12): 1449 (1997).] **PEER REVIEWED** PubMed Abstract
  • Both humans and rodents metabolize dichloroacetic acid to glyoxylate by oxidative dechlorination; the plasma half-life of the parent compound is 0.5-2 hours. A significantly greater percentage of the dose is excreted in the urine of rodents (about 20-30%), however, than by humans. Since only a negligible percentage of administered radiolabel is bound to plasma proteins or taken up by erythrocyte, dichloroacetic acid and its metabolites may be distributed to other tissues, although there is no direct evidence for this suggestion. Administration of repeated doses results in a marked decrease in the clearance of dichloroacetic acid from... .[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 280 (1995)] **PEER REVIEWED**
  • Carcinogenic and genotoxic effects of DCA have been most strongly associated with high doses where DCA metabolism is inhibited. This observation may indicate that DCA or a metabolite produced when the availability of the GSTZ pathway becomes limiting is the most actively toxic compound. ... The relative rate of DCA-induced inactivation of liver GSTZ was greater in rats than in mice or humans. GSTZ activity was greater in mouse liver than human liver. This could mean that humans are more sensitive to DCA toxicity than other species if toxicity is due to unmetabolized DCA.[U.S. EPA; Toxicological Review of Dichloroacetic Acid (CAS No. 79-43-6) In Support of Summary Information on the Integrated Risk Information System EPA 635/R-03/007 p.14 (August 2003) Available from a database querie of www.epa.gov/iris as of August 1, 2008] **PEER REVIEWED**
  • Data on DCA metabolism in humans are available because DCA has been used experimentally in the therapeutic treatment of several metabolic disorders. The data obtained support the hypothesis that DCA metabolism is similar in both humans and rodents. The occurrence of oxalic acid in the urine of DCA-treated patients indicates that DCA is oxidatively dechlorinated to glyoxylate, which is then converted to oxalate. In one child with congenital lactic acidosis, monochloroacetic acid was present in plasma in addition to oxalate and glyoxylate during the first four hours after the initial dose. Monochloroacetic acid concentrations were then below detection for the remainder of the observation period. Initially, the concentration of monochloroacetic acid in plasma exceeded that for glyoxylate, but not oxalate. These data indicate that in at least some individuals, the reductive dechlorination pathway can occur initially after DCA administration, but continued DCA metabolism occurs through the oxidative dechlorination pathway.[U.S. EPA; Toxicological Review of DIchloroacetic Acid (CAS No. 79-43-6) In Support of Summary Information on the Integrated RIsk Information System EPA 635/R-03/007p.4-5 (August 2003) Available from a database querie of www.epa.gov/iris as of August 1, 2008] **PEER REVIEWED**
  • Dichloroacetic acid (DCA) arises from the chlorination of drinking water and the metabolism of trichloroethylene (TRI) and is used therapeutically. The toxicity of TRI exposure is dependent on metabolism, and DCA has been proposed to be one contributor to this toxicity. Beyond the identification of some metabolites of DCA and some pharmacokinetic studies, little is known about the tissue distribution and enzymology of DCA metabolism. ... Data /is presented/ that indicate that DCA degradation occurs primarily in the cytosol. Low molecular weight components of cytosol are required for the reaction, including nicotinamide cofactor and glutathione (GSH). GSH plays a role in the removal of DCA from cytosol, although not through transferase mediated conjugation. In rat cytosol, the KM is approximately 0.3 mM, and the apparent Vmax approximates 12 nmoles/min/mg cytosolic protein. These results set DCA apart from other chlorinated compounds that are metabolized by the cytochrome P450 enzyme family.[Lipscomb JC, et al; Drug Metab Dispos 23 (11): 1202-5 (1995)] **PEER REVIEWED** PubMed Abstract
  • Dichloroacetic acid has been reported as a biotransformation product of methoxyflurane and dichlorvos, and it may occur in the tissues and fluids of animals treated with dichlorvos for helminthic infections.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 362 (2004)] **PEER REVIEWED**
  • Dichloroacetic acid is metabolized by both oxidative and reductive pathways. Both pathways lead ultimately to oxalate and carbon dioxide, glycolate and glyoxylate being probably intermediate metabolites in the reductive pathway. Reductive dechlorination of dichloroacetic acid to monochloroacetate, followed by glutathione conjugation to give thiodiacetic acid as the ultimate metabolite, has also been demonstrated. Oxalic, glycolic and thiodiacetic acids are the major urinary metabolites of dichloroacetic acid in both rats and mice. The metabolic reactions possibly involve free-radical intermediates.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V63 278 (1995)] **PEER REVIEWED**
  • GSTZ appears to be identical to maleylacetoacetate isomerase (MAAI), the enzyme in the pathway for tyrosine catabolism that converts the cis double bond in maleylacetoacetate (MAA) to the trans double bond in fumarylacetoacetate, using GSH as a cofactor ... There are species and age-related differences in the activity of GSTZ. ... Among humans there are known polymorphisms in GSTZ which may account for differences in the ability to metabolize dichloroacetic acid (DCA) and other halogenated compounds. The polymorphisms result from A/G transitions at nucleotides 94 and 124 of the coding region and T/C transitions at positions 23 and 245. The GSTZ variants are the products of the different combinations of the bases at the variant positions and were designated GSTZ1a-1a, GSTZ1b-1b, GSTZ1c-1c, GSTZ1d-1d, and GSTZ1e-1e . Analysis of a Caucasian (unselected, European Australian blood donors) population (141 subjects: 68 females and 73 males, ages 16 to 69) ... showed that the first three allele variants were present with frequencies of 0.09, 0.28, and 0.63, respectively. ......GSTZ1a-1a has been demonstrated to have different catalytic properties toward DCA than the other variants, including a 4-5-fold higher activity. However, excluding the GSTZ 1e-1e variant, the most active human GSTZ variants toward the catabolism of DCA appeared at the lowest frequency in the populations studied ...[U.S. EPA; Toxicological Review of DIchloroacetic Acid (CAS No. 79-43-6) In Support of Summary Information on the Integrated RIsk Information System EPA 635/R-03/007p.5-6 (August 2003) Available from a database querie of www.epa.gov/iris as of August 1, 2008] **PEER REVIEWED**
  • Glyoxylate formed from the metabolism of DCA may be routed though several different pathways. Transamination by peroxisomal alanine-glyoxylate transaminase forms glycine, which can be incorporated into proteins, used in the synthesis of serine, or degraded releasing carbon dioxide. Conversion to oxalate occurs via a (S)-2-hydroxyacid dehydrogenase such as lactate dehydrogenase. Glyoxylate can also be converted to glycolate by glyoxylate reductase. ... There may be other metabolic pathways for DCA. Oxalate, glycine, carbon dioxide, glycolate, monochloroacetic acid and thiodiacetic acid have been shown to be metabolites of DCA in rodents, although the relative amount of each seems to be species-specific ... . While urinary metabolites (glyoxylate, glycolate, oxalate, monochloracetic acid, and thiodiacetic acid) account for about 12-30% of the administered dose in rats and mice, carbon dioxide excretion may differ between these2 two species. ... Exhaled carbon dioxide generated from radiolabeled DCA was approximately 24 to 30% of a single administered dose in rats, but represented only 2% of the same dose in mice. However, a later study ... indicates that approximately 45% of a single administered dose of DCA in mice was exhaled as carbon dioxide in the first 24 hours after dosing. ... In both species the nonchlorinated acids were the primary metabolites detected in urine. Thiodiacetic acid concentrations were much greater than monochloroacetic acid, which was present in only trace quantities. To account for the production of metabolites that are not metabolically linked to glyoxylate, /it was/ ... proposed reductive dechlorination of DCA yielding monochloroacetic acid as an alternate metabolic pathway. The monochloroacetic acid is converted to thiodiacetic acid via glutathione conjugation.[U.S. EPA; Toxicological Review of DIchloroacetic Acid (CAS No. 79-43-6) In Support of Summary Information on the Integrated RIsk Information System EPA 635/R-03/007p.6-8 (August 2003) Available from a database querie of www.epa.gov/iris as of August 1, 2008] **PEER REVIEWED**
  • Oxalate is the primary urinary metabolite of dichloroacetic acid (DCA); it is formed by the oxidation of glyoxylate. In humans and animals, variable quantities of glyoxylate, glycolate, monochloracetic acid, and thiodiacetic acid are found in the urine. A fraction of the glyoxylate produced from DCA is oxidized to carbon dioxide and is exhaled. Carbon dioxide is also produced by the degradation of glycine formed from glycoxylate.[U.S. EPA; Toxicological Review of DIchloroacetic Acid (CAS No. 79-43-6) In Support of Summary Information on the Integrated RIsk Information System EPA 635/R-03/007 p.15 (August 2003) Available from a database querie of www.epa.gov/iris as of August 1, 2008] **PEER REVIEWED**
  • The disposition and elimination kinetics of (14C)dichloroacetic acid were studied in male Fischer 344 rats and B6C3F1 mice. In rats given 5, 20 or 100 mg/kg bw (14C)dichloro acetic acid by gavage, 23.9-29.3% of the dose was eliminated as carbon dioxide and 19.6-24.4% was excreted in the urine. Only 1.0-2.2% of the dose was excreted unchanged in the urine. The major urinary metabolites in rats were glyoxylic, oxalic and glycolic acids, which amounted to 10.5-15.0% of the dose, and thiodiacetic acid amounted to 6.3-6.8% of the dose. In mice given 20 and 100 mg/kg bw dichloroacetic acid by gavage, 2.2 and 2.4% of the dose was eliminated as carbon dioxide and 2.2-2.3% was excreted as unchanged dichloroacetic acid. The major urinary metabolites of dichloroacetic acid in mice were glyoxylic, oxalic and glycolic acids and thiodiacetic acid, which amounted to 13.4-18.4% and 7.9-12.3% of the dose, respectively.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 371 (2004)] **PEER REVIEWED**
  • The disposition of dichloroacetic acid (DCA) was investigated in Fischer 344 rats over the 48 hr after oral gavage of 282 mg/kg of 1- or 2-(14)C-DCA (1-DCA or 2-DCA) and 28.2 mg/kg of 2-DCA. DCA was absorbed quickly, and the major route of disposition was through exhalation of carbon dioxide and elimination in the urine. The disposition of 1- and 2-DCA at 282 mg/kg were similar. With 2-DCA, the disposition differed with dose in that the percentage of the dose expired as carbon dioxide decreased from 34.4% (28.2 mg/kg) to 25.0% (282 mg/kg), while the percentage of the radioactivity excreted in the urine increased from 12.7 to 35.2%. This percentage increase in the urinary excretion was mostly attributable to the presence of unmetabolized DCA, which comprised more than 20% at the higher dose and less than 1% at the lower dose. The major urinary metabolites were glycolic acid, glyoxylic acid, and oxalic acid. DCA and its metabolites accumulated in the tissues and were eliminated slowly. After 48 hr, 36.4%, 26.2%, and 20.8% of the dose was retained in the tissues of rats administered 28.2 and 282 mg/kg of 2-DCA and 282 mg/kg of 1-DCA, respectively. Of the organs examined, the liver(4.9-7.9% of dose) and muscle (4.5-9.9%) contained the most radioactivity, followed by skin (3.3-4.5%), blood (1.4-2.6%), and intestines (1.0-1.7%). One metabolite, glyoxylic acid, which is mutagenic, might be responsible for or contribute to the carcinogenicity of DCA.[Lin E LC, et al; J Toxicol Environ Health 38 (1): 19-32 (1993)] **PEER REVIEWED** PubMed Abstract
  • The disposition of dichloroacetic acid (DCA) was investigated in Fischer 344 rats over the 48 hr after oral gavage of 282 mg/kg of 1- or 2-(14C)-DCA (1-DCA or 2-DCA) and 28.2 mg/kg of 2-DCA. DCA was absorbed quickly, and the major route of disposition was through exhalation of carbon dioxide and elimination in the urine. ... The major urinary metabolites were glycolic acid, glyoxylic acid, and oxalic acid... One metabolite, glyoxylic acid, which is mutagenic, might be responsible for or contribute to the carcinogenicity of DCA.[Lin EL et al; J Toxicol Environ Health 38 (1): 19-32 (1993)] **PEER REVIEWED** PubMed Abstract
  • The primary metabolic pathway for dichloroacetic acid (DCA) involves oxidative dechlorination to form glyoxylate. This reaction, once thought to be microsomal Cytochrome P-450 mediated, has now been shown to be NADPH- and GSH-dependent and occurs predominantly in the cytosol. Recent work ... has identified a rat liver cytosolic enzyme, glutathione-S-transferase Zeta (GST Zeta), that catalyzes the conversion of DCA to glyoxylate. This enzyme is considered the rat ortholog of human GST zeta.[U.S. EPA; Toxicological Review of DIchloroacetic Acid (CAS No. 79-43-6) In Support of Summary Information on the Integrated RIsk Information System EPA 635/R-03/007p.4 (August 2003) Available from a database querie of www.epa.gov/iris as of August 1, 2008] **PEER REVIEWED**
  • The proposed formation of glyoxylic acid as an intermediate in the metabolism of dichloroacetic acid to oxalic acid, carbon dioxide and glycine was confirmed by the identification of (1-14C)- and (1,2-13C)glyoxylic acid as metabolites of (1-14C)- and (1,2-13C)dichloroacetic acid. The enzymes that catalysed this biotransformation were located in hepatic cytosolic fractions isolated from male Sprague-Dawley rats and from humans and required GSH, but not NADPH or NADH, for maximal activity. The rate of biotransformation to glyoxylic acid was decreased in hepatic cytosolic fractions from rats pretreated with 50 mg/kg bw dichloroacetic acid for 2 days compared with rats given water.[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/ENG/Classification/index.php, p. V84 375 (2004)] **PEER REVIEWED**
  • Trichloroacetate (TCA) and dichloroacetate (DCA) have been shown to be hepatocarcinogenic in mice when administered in drinking water. However, DCA produces pathological effects in the liver that are much more severe than those observed following TCA treatment in both rats and mice. To identify potential mechanisms involved in the liver pathology, the biotransformation of TCA and DCA was investigated in male Fischer 344 rats and B6C3F1 mice. Rodents were administered 5, 20, or 100 mg/kg (14C)TCA or (14C)DCA as a single oral dose in water. Elimination was examined by counting radioactivity in urine, feces, exhaled air, and carcass. Blood concentration over time curves were constructed for both TCA and DCA at the 20 and 100 mg/kg doses. Analysis of the data reveals two significant differences in the systemic clearance of TCA relative to DCA. First, DCA was much more extensively metabolized than TCA. More than 50% of any single dose of TCA was excreted unchanged in the urine of both rats and mice. In contrast, less than 2% of any dose of DCA was recovered in the urine as the parent compound. Second, while the blood concentration over time curves for TCA were similar in rats and mice, the blood concentrations of DCA were markedly greater in rats compared to those in mice, both when DCA was administered and when DCA resulted from metabolism of TCA. DCA was detected in the urine of TCA-treated animals and chloroacetate was found in the urine of DCA-treated animals. These metabolic products would be expected to arise from a free radical-generating, reductive dechlorination pathway... /Dichloroacetate/[Larson JL, Bull RJ; Toxicol Appl Pharmacol 115 (2): 268-77 (1992)] **PEER REVIEWED** PubMed Abstract

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Footnotes

1 Source: the NTP's CEBS database.

2 Source: the National Library of Medicine's Hazardous Substance Database, 02/28/2017.

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