Abstract
Resting cells (G0 cells) of the uterine surface epithelium in castrated mice began to synthesize DNA with high synchrony from 10hr after the injection of 50ng of estradiol-17β with or without 5.5μg of clomiphene citrate. Highly synchronized DNA synthesis in G0 cells elicited with estradiol was delayed approximately 5hr when the simultaneous administration of 0.5mg of progesterone was given. In Go cells of castrated mice which received 5.5μg of clomiphene or 55μg of clomiphene plus 50 ng of estradiol, DNA synthesis with partial synchrony began 15hr after the injection. The effects of estradiol were completely suppressed by the administration of 55μg 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 G0 cell-compartment.
