Development of an experimental model for studying bladder carcinogen metabolism using the isolated rat urinary bladder.

The isolated rat urinary bladder was used to study this organ's capacity to metabolize chemical carcinogens. In our experimental conditions, the urinary bladder carcinogen N-nitrosobutyl(4-hydroxybutyl)amine was oxidized to N-nitrosobutyl(3-carboxypropyl)amine. A time-dependent increase was observed in the amount of N-nitrosobutyl(3-carboxypropyl)amine formed and simultaneous disappearance of N-nitrosobutyl(4-hydroxybutyl)amine added, indicating that the bladder can metabolize N-nitrosobutyl(4-hydroxybutyl)amine to the metabolite considered responsible for tumor induction in the urinary bladder of laboratory animals. At 15, 30, 60, and 120 min the percentages of N-nitrosobutyl(3-carboxypropyl)amine formed were 11, 22, 36, and 64%, respectively, and 62, 48, 37, and 26% of N-nitrosobutyl(4-hydroxybutyl)amine remained unchanged. When N-nitrosodibutylamine was introduced into the isolated urinary bladder and incubated for 120 min, its oxidized metabolites N-nitrosobutyl(4-hydroxybutyl)amine and N-nitrosobutyl(3-carboxypropyl)amine were formed, amounting to, respectively, 0.13 and 0.06% of the substrate added. The glucuronide of N-nitrosobutyl(4-hydroxybutyl)amine was incubated in the isolated rat urinary bladder both as a buffer and as a urine solution in order to detect cellular and urinary beta-glucuronidase activity. In both systems N-nitrosobutyl(4-hydroxybutyl)amine released was about 1% at 4 h and this percentage did not increase at 6 h. N-Nitrosobutyl(3-carboxypropyl)amine was detectable at 2 h and reached 0.2% of the substrate incubated at 6 h. The results indicate that the urinary bladder may play a role in activating bladder carcinogens.