BIOLOGICAL PROPERTIES OF THREE OVULATION INDUCERS, STILBOESTROL, CLOMIPHENE AND F 6066

ABSTRACT In the anovulatory pseudopregnant rat, stilboestrol and F 6066 induced ovulation. The increased ovulation seen with clomiphene treatment was not statistically significant. In castrated rats, F 6066 and clomiphene are weak oestrogens relative to stilboestrol. The »anti-oestrogenic« action of clomiphene and F 6066 was demonstrated by their ability to block the uterotrophic activity of stilboestrol in castrated rats. Clomiphene proved a more potent anti-oestrogen than F 6066. In rats, stilboestrol and clomiphene are relatively potent, orally active contraceptives, and they are equally potent given before or after ovulation. F 6066, on the other hand, is a weak contraceptive. Stilboestrol is reported to block progesterone-induced endometrial proliferation in the rabbit. F 6066 also has this property while clomiphene, at the doses tested, does not. It is concluded that clomiphene and F 6066 have similar oestrogenic profiles with different potencies. Further, there appears to be no potency relationship from test to test. Ovulation induction in pseudopregnant rats by F 6066 and clomiphene does not appear to be related to their antioestrogenic activities.