Assessment of the progestagenic and oestrogenic activity of compounds by their effect on implantation in rats with diapausing embryos.

The oestrogenic, progestagenic and mixed oestrogenic--progestagenic activities of various compounds were assessed by their effects on implantation and its delay in the ovariectomized rat. Progesterone, norgestrel and 17 alpha-(2-butynyl)-17 beta-hydroxyestra-4,9,11-trien-3-one (R3852-3) were investigated. Progesterone and norgestrel proved to be progestagens with little or no inherent oestrogenic activity, while R3852-3 appeared to have both progestagenic and oestrogenic activity. The oestrogenic activity of R3852-3 was verified by using an Allen--Doisy type of assay system.