Virilizing activities of various steroids in female rat fetuses.

Virilizing activities of nineteen steroids were examined by a method measuring the abridgment of urovaginal septum length of female rat fetuses directly under microscope, following oral administration of the steroids to the mothers for 4 days during the late period of gestation. The characteristics of the virilizing activities of the steroids seemed to depend on their chemical structures. No virilizing activities were observed in progesterone, retroprogesterone, chlormadinone acetate and nandrolone phenpropionate. The introduction of 6-methyl and 17-acetoxy groups into progesterone exhibited a marked virilizing activity. With testosterone and its derivatives, the introduction of 17alpha-ethynyl group into testosterone slightly decreased the virilizing activity compared with the parent compound. On the contrary, the introduction of [3, 2-C] pyrazole ring in addition to the saturation of A-ring strikingly increased the virilizing activity. The most active virilizing steroid in this group was stanozolol followed by oxymetholone, methyl-testosterone and dimethysterone. Testosterone propionate was assumed to be less active than methyltestosterone by this route. With 19-nortestosterone derivatives, the virilizing activities of compounds with 17alpha-ethynyl group were moderate, but the presence of 17alpha-ethyl group caused a marked increase of virilizing activity. While, nandrolone phenpropionate with long side chain at C-17 exhibited no significant virilizing activity. The present results show the possibility of the evaluation on a potential virilizing activity of compounds in the female fetus, and also suggest that a dossociation between the virilizing activity and the androgenic activity may exist among some compounds.