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

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.

Benzo(a)pyrene metabolism in bovine aortic endothelial and bovine lung fibroblast-like cell cultures.

The metabolism of [3H]benzo(a)pyrene ([3H]BP) in bovine aortic endothelial and bovine lung fibroblast-like cells in vitro was investigated. Both cell types metabolized BP to organic solvent-extractable and water-soluble metabolites. The major organic solvent-extractable metabolites were 9-hydroxy-benzo(a)pyrene and 3-hydroxybenzo(a)pyrene; 7,8-dihydro-7,8-dihydroxybenzo(a)pyrene, 9,10-dihydro-9,10-dihydroxy-benzo(a)pyrene, and BP quinones were also formed. No glucuronide or sulfate conjugates of BP metabolites were detected. When exposed to [3H]-3-hydroxybenzo(a)pyrene, both cell types metabolized this phenol to water-soluble derivatives, probably through oxidation rather than conjugation of the molecule. These results demonstrate that endothelial cells metabolze BP to a proximate carcinogenic derivative, the 7,8-dihydrodiaol. Thus, efforts to predict the biological effects of hydrocarbons of an organism must take into account possible metabolic activation by endothelial cells as well as by other target tissues. The formation of unconjugated, phenolic hydrocarbon derivatives by bovine cells suggests their use as a model system for studying the contribution of phenols to the induction of biological effects by hydrocarbons.