Different susceptibilities of the urinary bladder epithelium of animal species to three nitroso compounds.

Differences in the susceptibilities of the urinary bladder epithelium of Wistar rats, ICR mice, Syrian golden hamsters, and Hartley guinea pigs to three N-nitroso compounds, N-butyl-N-(4-hydroxybutyl)nitrosamine, N-ethyl-N-(4-hydroxybutyl)nitrosamine, and N-butyl-N-(3-carboxypropyl)nitrosamine, were examined histologically. The urinary bladder epithelium of rats was the most susceptible to all three compounds, and especially to N-ethyl-N-(4-hydroxybutyl)nitrosamine, and bladder cancers developed in all the rats given this compound. The bladder epithelium of mice was less susceptible than that of rats but, although the incidence of cancer was lower than in rats, that of cancer with invasion was higher. Hamsters were far less susceptible than mice, and cancer developed only in 3 of 41 animals given N-ethyl-N-(4-hydroxybutyl)nitrosamine. Guinea pigs were the least susceptible of the 4 species and no tumors were found. Hisotlogically, most of the tumors induced in rats and mice were transtitional cell carcinomas. The incidence of undifferentiated carcinoma was higher in mice than in rats and cellular or structural atypism of the cancer was also greater in mice. Cancers induced in hamsters were all transitional cell carcinomas showing invasion.