Effects of intravesical instillation of antitumor drugs on the induction of preneoplastic bladder lesions in rats.

The effects of adriamycin (ADR) and mitomycin C (MMC) as inhibitors of the development of bladder tumors in rats were studied. Six-week-old female F344 rats were divided into nine groups, five of which received 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) in their drinking water for the first 4 weeks, no treatment for 1 week, and then intravesical instillation once a week of ADR, MMC, or physiological saline or no instillation (no catheterization) for 12 weeks. The other four groups received no BBN for the first 5 weeks of the experiment and then received ADR, MMC, or physiological saline as above for 12 weeks. The bladders were examined by light microscopy 17 weeks after the beginning of the experiment. Results showed that development of preneoplastic lesions induced in the bladders of the rats by BBN was stimulated by subsequent instillation of ADR or MMC. This result suggests that ADR and MMC have promoting activities in bladder carcinogenesis of rats.