[Effect of age, castration and pregnancy on carcinogenesis, induced by 1,2-dimethylhydrazine, in CBA mice]

Subcutaneous injection of 1,2-dimethylhydrazine into female CBA mice once a week resulted in the development of tumours of the colon, anal region, uterus and liver. In 12-13-month-old mice treated with DMH an earlier appearance (week 8) of uterine sarcomas and more rapid increase in the incidence of tumours of the anal region were noted as compared to 3-month-old mice. In pregnant females treated with DMH a statistically significant decrease in the uterine sarcoma incidence was observed (10.3% versus 48.3% in nonpregnant). Pregnancy exerted no effect on the incidence of tumours at other sites. Castration did not affect the time of appearance and the incidence of tumours of any site.