N-NITROSOMETHYLUREA-INDUCED CARCINOGENESIS IN THE PROGENY OF MALE-RATS OF DIFFERENT AGES

Three-month-old male and 3-month-old female LIO rats as well as 25-month-old males and 3-month-old females were mated and at the age of 3 months their progeny were exposed to a single intravenous injection of N-nitrosomethylurea (MNU) at the dose of 20 mg/kg of body weight or solvent. Animals were under observation during 18 months after injection of the carcinogen. There was no significant difference in spontaneous tumor incidence between progeny of young and old male rats. At the same time, the susceptibility to the carcinogenic effect of NMU in the male and female progeny of old males was slightly but significantly increased in comparison to the progeny of young males. Mesenchymal kidney tumors were discovered in the NMU-treated male progeny of old males but not in the male progeny of young male rats. In females, the incidence of mesenchymal kidney tumors in the NMU-treated progeny of young and old males was 7% and 20%, respectively, and the mean survival times of these tumor-bearing rats was 4 months shorter in the last group. The data obtained are in agreement with the observation on germ-line transgeneration transmission of predisposition to carcinogenesis.