Effect of azathiopurine and OK-432 on urinary bladder carcinogenesis in rats.

The effect of azathiopurine and OK-432 on bladder carcinogenesis in rats was evaluated using the carcinogens, N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) and N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT). Azathiopurine did not affect FANFT bladder carcinogenesis in any treatment. By contrast, when azathiopurine was fed simultaneously with BBN there was a significant increase in the incidence of bladder tumors, although it had no effect if administered before or after BBN. Short-term administration (8 weeks) of OK-432 subcutaneously before, during, or after BBN did not affect bladder carcinogenesis, but if OK-432 was begun after BBN and continued until the end of the experiment, the incidence of BBN-induced bladder tumor was significantly reduced. No bladder lesions were observed in control rats or in rats receiving only azathiopurine or OK-432.