Formation of glucuronic acid conjugates of 7,12-dimethylbenz(a)anthracene phenols in 7,12-dimethylbenz(a)anthracene-treated hamster embryo cell cultures

Abstract

Secondary cultures of hamster embryo cells exposed to 0.5 nmol [G-3H]7,12-dimethylbenz(a)anthracene (DMBA) per ml medium metabolized more than 90% of the DMBA within 48 hr. Samples of medium were extracted with chloroform, methanol, and water. The chloroform phases contained about one-third of the DMBA metabolites; the major chloroform-extractable metabolite was 8,9-dihydro-8,9-dihydroxy-7,12-dimethylbenz(a)anthracene. Beta-glucuronidase treatment of the aqueous methanol-soluble metabolites converted almost one-half of them to chloroform-soluble metabolites, of which more than 80% were identified as phenolic derivatives of DMBA. Similar metabolite profiles were obtained by treating the medium with beta-glucuronidase before chloroform extraction. Separation of the methyl group-hydroxylated derivatives of DMBA from the phenolic derivatives was accomplished by high-pressure liquid chromatography. Small amounts of hydroxymethyl derivatives were detected only in the chloroform-extractable material, whereas DMBA phenols were the major component of the beta-glucuronidase-released mateirla. These results indicate that the major pathway of DMBA metabolism in hamster embryo cells is oxidation of the aromatic rings and not oxidation of the methyl groups.