[Effect of 1,2-dimethylhydrazine on the estrous cycle in different strains of mice]

CBA, C3HA, C57Bl, Balb/c and DBA female mice received 20 subcutaneous weekly injections of 1,2-dimethylhydrazine in the dose of 8 mg/kg body weight. Estrous cycles were studied in vaginal smears taken 5, 10, 15 and 20 weeks after the 1st DMH injection. In CBA strain susceptible to DMH induction of uterine sarcomas a persistent estrus was observed in 50% of mice after 5 to 10 DMH injections. In C3HA, C57B1, Balb/c and DBA strains resistant to the DNH induction of uterine sarcomas persistent estrus was not observed; the majority of these mice retained a normal estrus cycle. Persistent diestrus which was absent in susceptible CBA mice was found in these resistant strains. No CBA females with a normal estrous cycle were observed after the beginning of DMH treatment. The differences in the estrous cycle found in the mouse strains treated with DMH may partly explain the observed strain differences in the susceptibility to the DMH induction of uterine sarcomas.