Initiation-stage enhancement by uracil of N-ethyl-N-hydroxyethylnitrosamine-induction of kidney carcinogenesis in rats.

The present study was conducted to clarify the effects of N-ethyl-N-hydroxyethylnitrosamine (EHEN) and uracil in combination on renal carcinogenesis in female F344 rats. Group 1 animals (n = 30) received a 3-week simultaneous administration of 0.05% EHEN and 3% uracil, and group 2 (n = 26) 0.05% EHEN with a lower 1.5% dose of uracil. Group 3 (n = 30) was treated with 0.05% EHEN alone and group 4 (n = 28) received only 3% uracil for 3 weeks. In all the above four groups, the rats were given basal diet and water without chemical addition for a 48-week period after the 3-week treatment period. Group 5 (n = 33) received no chemicals for the entire 52 weeks. At the end of week 52, renal adenocarcinomas were found in 53%, 31% and 13% of the rats in groups 1, 2, and 3, respectively. The present study thus demonstrated that simultaneous administration of uracil enhances the occurrence of EHEN-induced renal adenocarcinomas in rats.