Estrogen modification of 1,2-dimethylhydrazine carcinogenesis in C3HA mice

Considerable strain differences were reported in our previous studies in the induction by 1,2-dimethylhydrasine (DMH) of uterine sarcoma and hemorrhagic ovarian lesion (HOL) in mice: the incidence of the former was high and that of the latter was low in CBA mice while the reverse was observed in C3HA mice. The present study confirmed the above observation in that C3HA mice treated with DMH developed high incidence (59%) of HOL and no uterine sarcoma. Combined treatment of C3HA mice with DMH and estradiol dipropionate (EP) completely inhibited the induction of HOL and increased the incidence of uterine sarcomas from naught to 28%. EP significantly decreased (from 61 to 19%) the incidence of clitoral gland tumors and somewhat increased the frequency of liver epithelial tumors and colon tumors. It is suggested that the strain differences in the induction by DMH of uterine sarcoma and HOL may be due rather to differences in the strain hormonal status than to the differences in the susceptibility to carcinogen.