Enhancing effect of allopurinol on the induction of bladder cancer in rats by n-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide.

The effects of allopurinol on the induction of bladder cancer by N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT), excretion of urinary tryptophan metabolites, hepatic nitroreductase activity, and the acid-soluble thiol content of liver and blood in weanling female Fischer rats were investigated. Four groups of rats were given normal diet or normal diet supplemented with 0.005% allopurinol, 0.188% FANFT, or 0.005% allopurinol-0.188% FANFT. Transitional cell carcinomas appeared in 3 of 30 rats (10%) at 15 weeks and in 7 of 44 rats (16%) at 20 weeks in the FANFT-treated group; the carcinomas appeared in 14 of 35 rats (40%) at 15 weeks and in 27 of 50 rats (54%) at 20 weeks in the FANFT-allopurinol-treated group. Growth rate was not affected by allopurinol and FANFT. Allopurinol alone caused no morphological change in the epithelial cells of the urinary bladder but decreased hepatic cytosol nitroreductase activity. FANFT alone had no effect on hepatic cytosol or microsomal nitroreductase activity but increased hepatic and blood acid-soluble thiol content. FANFT increased the urinary excretion of anthranilic acid glucuronide, kynurenine, acetylkynurenine, and 3-hydroxykynurenine and decreased indican and o-aminohippurate excretion. Allopurinol did not alter the effects of FANFT on the acid-soluble thiol content of liver and blood or the excretion of urinary tryptophan metabolites.