Effect of quercetin on two-stage carcinogenesis of the rat urinary bladder.

The initiating and promoting effects of quercetin on urinary bladder carcinogenesis in male F344 rats were examined histopathologically. No tumor or hyperplasia were observed in rats given 5.0% quercetin as initiator in the diet for 4 weeks followed by 0.001% N-butyl-N-(4-hydroxybutyl) nitrosamine (BHBN) for 29 weeks. Moreover, administration of 5.0% quercetin diet for 25 weeks after initiation with 0.01% BHBN for 4 weeks did not promote urinary bladder carcinogenesis. Furthermore, no lesions were detected in rats given 5.0% quercetin diet only. These results suggest that quercetin is not carcinogenic to rat urinary bladder.