Metabolism of benzo(a)pyrene with isolated hepatocytes and the formation and degradation of DNA-binding derivatives.

The metabolism of [Wlbenzo(a)pyrene with isolated hepatocytes from 3-methylcholanthrene-treated rats was examined with the aid of high pressure liquid chromatography. Covalent binding of [SHlbenzo(a)pyrene metabolites to the intracellular DNA was investigated. The effects of (Ynaphthoflavone, salicylamide, trichloropropene oxide, and diethylmaleate, individually or combined, on the metabolism and covalent DNA binding of benzo(a)pyrene were determined. The results indicate that the initial organic-soluble metabolites were arene oxides, phenols, quinones, and dihydrodiols and that these were subsequently converted to relatively polar, organic-soluble nonconjugated and sulfateconjugated metabolites and to aqueous-soluble nonconjugated and glucuronideand glutathione-conjugated metabolites. ru-Naphthoflavone inhibited the formation of benzo(a)pyrene metabolites that covalently bound to hepatocyte DNA, while the binding was stimulated by salicylamide, trichloropropene oxide, or diethylmaleate. Our observations indicate that benzo(a)pyrene-oxide hydration and glutathione conjugation, and glucuronide and sulfate conjugation of hydroxylated benzo(a)pyrene metabolites operate in concert to detoxify electrophilic DNA-binding benzo(a)pyrene metabolites in isolated hepatocytes. The degree of covalent binding of benzo(a)pyrene to the nuclear DNA of isolated hepatocytes seems thus to be correlated with the production of electrophilic benzo(a)pyrene metabolites and the rate of their disposal by epoxide hydratase and conjugation reactions.