Dose-response study of N-nitrosomethyl(2-hydroxypropyl)amine-induced nasal cavity carcinogenesis in rats.

Dose response to the carcinogenic activity of N-nitrosomethyl(2-hydroxypropyl)amine (MHP) was investigated for the nasal cavity of male Wistar rats. MHP dissolved in 0.9% saline was administered intraperitoneally once a week for 12 weeks at doses of 0, 4.4, 8.8 and 17.6 mg/kg body weight, and all surviving animals were sacrificed 26 weeks after the beginning of the experiment. Hyperplasias, papillomas and squamous cell carcinomas were induced. Hyperplasias could be divided into flat, protruding and downgrowth types and were observed in respiratory and squamous epithelial regions. Papillomas and squamous cell carcinomas developed in the respiratory region, and the incidence of the latter reached 83% in rats which received the highest dose of MHP. These results indicate that MHP shows its carcinogenic activity of the nasal cavity by the development of squamous cell carcinomas.