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National Institute of Environmental Health Sciences

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Your Environment. Your Health.

Publication Detail

Title: N-acetylation of the heterocyclic amine batracylin by human liver.

Authors: Stevens, G J; Payton, M; Sim, E; McQueen, C A

Published In Drug Metab Dispos, (1999 Sep)

Abstract: Batracylin (8-aminoisoindolo[1,2-b]quinazolin-12(10 H)-one; BAT) is a heterocyclic amine that exhibits antitumor activity in a number of in vivo and in vitro models. The acetyl product has been implicated in BAT toxicity in animals, cells, and bacteria. The ability of human N-acetyltransferase (NAT) to form this product was investigated. Nine human liver samples were analyzed for NAT1 and NAT2 genotypes. Seven of the samples possessed at least one NAT1*4 allele. Three samples contained one or more NAT2*4 allele and were classified as rapid acetylators. The remaining six had two alleles associated with the slow phenotype. NAT activities were evaluated with BAT, sulfamethazine (SMZ), a preferential substrate for human NAT2, and p-aminobenzoic acid, a substrate for NAT1. BAT activities in the nine donor samples ranged from 14.9 to 0.56 nmol/min/mg. The mean apparent K(m) values in rapid acetylators for BAT, SMZ, and p-aminobenzoic acid were 6.59 +/- 3.21, 278 +/- 69.4, and 31.2 +/- 12.5 microM, respectively. The apparent K(m) values for slow acetylators did not differ from the rapid acetylator phenotype. However, a significant difference in the apparent V(max) for BAT and SMZ was observed between rapid and slow acetylators. Comparing the apparent intrinsic clearance (V(max)/K(m)) for BAT and SMZ, a significant correlation (r(2) = 0.97, p <.001) was observed. These data demonstrate that BAT N-acetylation is similar to SMZ, and suggests that BAT is a preferential substrate for human NAT2. Thus, rapid acetylators would be more likely to develop toxicity when exposed to this drug.

PubMed ID: 10460792 Exiting the NIEHS site

MeSH Terms: 4-Aminobenzoic Acid/metabolism; Acetylation; Adult; Aged; Antineoplastic Agents/metabolism*; Arylamine N-Acetyltransferase/biosynthesis; Arylamine N-Acetyltransferase/genetics; Arylamine N-Acetyltransferase/metabolism; Child, Preschool; Cloning, Molecular; Cytosol/metabolism; DNA Primers; Female; Genotype; Humans; Kinetics; Liver/metabolism*; Male; Middle Aged; Quinazolines/metabolism*; Sulfamethazine/metabolism

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