Effect of vitamin A acetate on urinary bladder carcinogenesis induced by N-butyl-N-(4-hydroxybutyl)nitrosamine in rats.

The effect of vitamin A acetate on the urinary bladder carcinogenicity of N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) was determined in male Wistar rats. Vitamin A acetate at the dose administered induced no changes in the urinary bladder or other organs when administered without the carcinogen. However, hypervitaminosis A inhibited keratinization and squamous metaplasia in bladder lesions induced by BBN, and the incidence of transitional cell carcinoma and papilloma of the urinary bladder was significantly reduced at a dose greater than 100 IU/g diet (P less than 0.02). The present experiment suggests that for the urinary bladder epithelium of rats hypervitaminosis A reduced susceptibility to the tumorigenicity of BBN.