Methyl cholanthrene applied locally to the vagina of ovariectomized mice antagonizes the vaginal cornification produced by 0·2μg oestradiol. Much larger doses of oestradiol abolish this effect. Previous exposure to the carcinogen does not produce this antagonism. The carcinogen prevents the production of vaginal mucification in pregnant mice and also in mice treated with 750 μg progesterone and 0·05 μg oestradiol. Again, previous exposure to the carcinogen does not produce this antagonism.
The effects of testosterone on the seminal vesicle in the rat and of deoxycorticosterone on the endometrium of the rabbit are antagonized by the local implantation of methyl cholanthrene.
These results suggest that there is competitive antagonism between methyl cholanthrene and the steroid hormones investigated. The possible significance of these findings is discussed.