To test the hypothesis that activation of bladder carcinogens occurs intracellularly by enzymes associated with the transitional epithelial cells of the bladder, the metabolic capabilities of these cells will be investigated. The bioactivation of the human urinary bladder carcinogen, 4-aminobiophenyl(ABP); 4-nitrobiphenyl(NBP); and the experimental bladder carcinogen N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide (FANFT) will be examined using normal human and rat urothelial cells. The nature of intermediate(s) that are activated by the urothelial cells will be assessed by testing the cytosolic and microsomal fractions for certain enzymatic activities such as N-oxidation, nitroreduction, N-glucuronidation, sulfation, acetylation, deacetylation and N--O transacylation; and by identifying the DNA-carcinogen adducts. The DNA-carcinogen adducts will be isolated from cultured human urothelial cells after treatment with tritium labeled ABP, NBP, 4-nitrosobiphenyl, N-hydroxylaminobiphenyl or its N-glucuronide conjugate. The profiles of the adducts generated from cultured cells will be compared with those obtained by chemical interaction of N-hydroxylaminobiphenyl or its N-glucuronide derivative with calf thymus DNA in vitro at pH 5.0. The formation of, and biological reactivities of the proximate metabolites will be assessed by urothelium-mediated mutagenicity tests in Salmonella typhimurium strains. A long range objective of this project is to understand which of the adducts and enzymes play a determinate role in the initiation of human cancers caused by ABP and its related analogs; and to find out the metabolic factors responsible for the observed differences in susceptibility to ABP-induced bladder carcinogenesis between rats and humans.
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