Effects of clomiphene citrate and progesterone on resting and proliferative cell-populations in resting and proliferative cell-populations in mouse uterine epithelium.

Resting cells (GO cells) of the uterine surface epithelium in castrated mice began to synthesize DNA with high synchrony from 10 hr after the injection of 50 ng of estradiol-17beta with or without 5.5 mug of clomiphene citrate. Highly synchronized DNA synthesis in GO cells elicited with estradiol was delayed approximately 5 hr when the simultaneous administration of 0.5 mg of progesterone was given. In GO cells of castrated mice which received 5.5 mug of clomiphene or 55 mug of clomiphene plus 50 ng of estradiol, DNA synthesis with partial synchrony began 15 hr after the injection. The effects of estradiol were completely suppressed by the administration of 55 mug of clomiphene. It is suggested that the inhibitory action of clomiphene may be due to the competitive blocking of estrogen binding, while progesterone suppresses the estrogen-induced DNA synthesis of the surface epithelium and transfers them to the GO cell-compartment.