Oxidation and subsequent glucuronidation of 3,4-benzopyrene in everted intestinal sacs in control and...

The metabolism of 3,4-benzopyrene in the wall of isolated everted intestinal sacs was studied in control and 3-methylcholanthrene induced rats. The luminal (outer) side of the intestine was perfused with a 100-mumol/l concentration of 3,4-benzopyrene in Krebs-Ringer's bicarbonate buffer supplemented with 5% glucose and 2% albumin. A thin-layer chromatography assay method was used to analyze benzo(a)pyrene metabolites. After the pretreatment of rats with 3-methylcholanthrene, the amount of hydroxylated metabolites was about 1.5-fold and the amount of consequent glucuronides was about 3-fold in comparison with the controls. 3-Methylcholanthrene induction mainly increased the production of 3- and 9-hydroxybenzopyrene and dihydrodiols. The glucuronidation of 3- and 9-hydroxybenzopyrene was enhanced by 3-methylcholanthrene but the conjugation of dihydrodiols was nonresponsive to induction. Only small amounts of glucuronides were present in the inner (serosal) side of the intestinal sac. The data suggest different responses of various benzo(a)pyrene metabolites to induction in the intestinal mucosa. In addition to metabolic functions the intestinal mucosa may function as an excretory organ for polycyclic aromatic hydrocarbons entering the body.