The oestrogenic and anti-oestrogenic activity of some synthetic steroids and non-steroids

A number of steroids inhibited oestradiol-17β stimulated tetrazolium reduction when given intravaginally at the same time as the oestrogen, but none of them was as potent as dimethylstilboestrol (DMS). The most effective compounds possess free or esterified hydroxyls at 3 and 17 and to this extent resemble oestradiol-3:17β. All of the steroids which were anti-oestrogenic were also to some extent oestrogenic in that they increased vaginal tetrazolium reduction, uterine weight or uterine epithelial mitosis, when given in high doses subcutaneously. Although there were exceptions the more potent anti-oestrogens also tended to be the more potent oestrogens. Of the non-steroids, MRL-41 was oestrogenic but not anti-oestrogenic, SC7801 was a relatively potent anti-oestrogen but was only weakly oestrogenic. MRL-37 was weakly anti-oestrogenic locally. It significantly increased tetrazolium reduction uterine weight and uterine epithelial mitosis at 1000 μg subcutaneously, but higher doses increasingly depressed these responses.