Metabolism of benzo[A]pyrene in hamster embryo cells. Effect of the concentration of benzo[A]pyrene on its metabolism.

The metabolism of benzo[a]pyrene (BP) by hamster embryo cells was studied. The production of water-soluble metabolites, shown to be conjugates with glucuronic acid, depended on BP concentration. With increased BP concentration the amount of glucuronic acid conjugates increased, but the proportion of conjugates in BP or its metabolites present in the medium decreased. The metabolites extracted with ethylacetate were trans-7,8-dihydrodiol-BP (7,8-dihydrodiol) and trans-9,10-dihydrodiol-BP (9,10-dihydrodiol), but large peaks of phenolic metabolites were found by high pressure liquid chromatography (HPLC) after digesting the medium with beta-glucuronidase. Therefore, BP is metabolized to oxygenated forms, and of these, most of the phenolic metabolites and parts of the dihydrodiols are conjugated with glucuronic acid. The proportions of dihydrodiols to phenols, estimated by HPLC after beta-glucuronidase digestion, decreased when the BP concentration was decreased. The results suggest that dihydrodiols are less readily glucuronidated than phenols and so may be metabolized further to metabolites other than glucuronic acid conjugates.