METABOLISM AND BINDING OF BENZO(A)PYRENE AND 2-ACETYLAMINOFLUORENE BY SHORT-TERM ORGAN-CULTURES OF HUMAN AND RAT BLADDER

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 42  (2) , 642-648
Abstract
The ability of organ cultures of normal human and rat bladder to metabolize the polycyclic hydrocarbon, benzo(a)pyrene (BP), and the arylamine, 2-acetylaminofluorene, was studied. Cultures were maintained for 0-6 days in a chemically defined medium before incubation with [3H]BP (0.3-0.5 .mu.M) or 2-[14C]acetylaminofluorene (18-25 .mu.M) for 24 h. Ethyl acetate-soluble and water-soluble metabolites were produced from both compounds by both species. The ethyl acetate extracts from [3H]BP-treated human cultures contained 9,10-dihydro-9,10-dihydroxybenzo(a)pyrene, 7,8-dihydro-7,8-dihydroxybenzo(a)pyrene and 3-hydroxybenzo(a)pyrene. Rat bladder cultures produced similar metabolites but in slightly different proportions. Ethyl acetate-soluble products of 2-[14C]acetylaminofluorene from human cultures contained 7-hydroxy-2-acetylaminofluorene, 9-hydroxy-2-acetylaminofluorene, 2-aminofluorene and N-hydroxy-2-acetylaminofluorene. Rat bladder cultures produced similar metabolites but 2-aminofluorene was found in relatively higher proportion. Hydrolysis by .beta.-glucuronidase of the water-soluble products produced from both carcinogens gave ethyl acetate-extractable derivatives. These hydrolyzable glucuronide conjugates were relatively more abundant following metabolism of the carcinogens by the rat than by the human cultures. Covalent binding to DNA occurred with [3H]BP in both human (19.7 .+-. 13 pmol/mg DNA) and rat cultures (22.8 .+-. 8.6 pmol/mg DNA). As with other human tissues, considerable variation (50-fold) was observed between individuals. Human and rat bladder epithelium can metabolize known potent carcinogens and, in the case of BP, can effect covalent binding between the products of metabolism and the urothelial cell DNA. In theory, carcinogenesis in the urinary bladder could thus be initiated by carcinogens produced or excreted in the urine without the necessity for their prior metabolism elsewhere in the body.