Characterization of benzo[a]pyrene metabolism and related cytochrome P‐450 isozymes in Syrian hamster livers

Abstract

Cytochrome P‐450 monooxygenases of golden Syrian hamsters were characterized with respect to benzo[a]pyrene metabolism. Male hamsters were treated with phenobarbital, 3‐methylcholanthrene, dexamethasone, benzoflavone, or ethanol, and the activity of aryl hydrocarbon hydroxylase and benzo[a]pyrene activation was determined by mutagenicity testing in hepatic microsomes. Aryl hydrocarbon hydroxylase activity was induced markedly by treatment with phenobarbital but not with 3‐methylcholanthrene, nor with other chemicals. The degree of benzo[a]pyrene activation on mutagenicity testing was significantly elevated by treatment with 3‐methylcholanthrene and phenobarbital but was reduced with dexamethasone. Immunoinhibition of these activities and Western blotting of hepatic microsomes using antibodies against cytochrome P‐450 isozymes suggested that the isozymes responsible for benzo[a]pyrene metabolism in Syrian hamsters belong to the CYP1A, CYP2A, and CYP3A families, a result that differs from observations in rats.