The effect of single dose N-methyl-N-nitrosourea on bladder carcinogenesis by N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide in rats.

The effect of a single intravesical dose of N-Methyl-N-Nitrosourea (MNU) on bladder carcinogenesis in Fischer rats by a suprathreshold dose of N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide (FANFT) was studied. Animals were sacrificed periodically during the course of the study and the experiment was terminated 50 weeks. Carcinomas were first noted in the MNU + FANFT group at 35 weeks versus 37 weeks for the group receiving FANFT alone. At 50 weeks, carcinomas were seen in 40 of 49 animals in the MNU + FANFT group and in 40 of 48 animals in the FANFT group. Of the animals developing bladder carcinomas 50 per cent receiving MNU + FANFT and 32 per cent receiving FANFT had high grade tumors. Six per cent of the animals receiving MNU alone developed bladder carcinomas whereas none was seen in a control group. In this system, the addition of an inducing dose of MNU did not alter the induction rate or results of carcinogenesis by FANFT. There was a tendency for higher grade tumors in those animals receiving the inducing dose of MNU.