NEOPLASTIC AND NONNEOPLASTIC URINARY-BLADDER LESIONS INDUCED IN FISCHER-344 RATS AND B6C3F HYBRID MICE BY N-NITROSODIPHENYLAMINE

N-Nitrosodiphenylamine was administered to groups of 50 rats and mice of both sexes in a standard NCI bioassay. The compound was mixed with feed and given ad libitum for 2 years at a maximally tolerated dose. Urinary bladder tumors, characterized as transitional cell carcinomas, were observed in 40% of male rats and 90% of female rats. In the mice, there were few urinary bladder tumors, but a high incidence of nonneoplastic bladder lesions. The possible implications of these results with a N-nitroso compound previously considered noncarcinogenic are discussed. © 1979.