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National Institute of Environmental Health Sciences

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Your Environment. Your Health.

Publication Detail

Title: Ah receptor involvement in mediation of pyruvate carboxylase levels and activity in mice given 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Authors: Ryu, B W; Roy, S; Sparrow, B R; Selivonchick, D P; Schaup, H W

Published In J Biochem Toxicol, (1995 Apr)

Abstract: The arylhydrocarbon receptor (AhR) plays a central role in mediating 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity in animals. The investigations described here provide evidence that support a role for the AhR in TCDD-mediated pyruvate carboxylase (PC) level/activity reductions in mice. Pyruvate carboxylase plays a pivotal role in gluconeogenesis and in supplying carbon units for the citric acid cycle. Delivered ip in a corn oil carrier, TCDD suppresses PC activity/amount at doses as low as 1 microgram/kg in responsive C57BL/6J(Ahb/b) mice. Corn oil alone injected ip into mice at 4 mL/kg appears to be an inducer that increases the amount and activity of PC. However, TCDD suppresses this induction. In the Ahb/b mouse, PC levels and activity are reduced to 10% of control values at a dose of 75 micrograms/kg. A time-course experiment shows that the PC reductions are apparent within 16 hours post-TCDD exposure. Here we report investigations on the PC/TCDD response using a congenic C57BL/6J(Ahd/d) mouse strain having an AhR with a low affinity for TCDD. If the PC/TCDD response is AhR mediated, the congenic mouse strain (Ahd/d) would require much higher doses of TCDD to suppress PC. In the Ahd/d mice, we observe that an approximately 60-fold increase in TCDD dose is necessary to produce a PC/TCDD effect. We also find that in Ahd/d mice, corn oil does not induce an increase in PC activity/amounts, as reported for Ahb/b mice.

PubMed ID: 7562952 Exiting the NIEHS site

MeSH Terms: Animals; Blotting, Western; Corn Oil/pharmacology; Cytosol/enzymology; Kinetics; Lactates/blood; Liver/drug effects; Liver/enzymology*; Mice; Mice, Inbred C57BL; Mice, Inbred Strains; Polychlorinated Dibenzodioxins/pharmacology*; Pyruvate Carboxylase/biosynthesis; Pyruvate Carboxylase/metabolism*; Receptors, Aryl Hydrocarbon/physiology*; Species Specificity; Time Factors

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