EFFECTS OF OESTROGEN AND PROGESTERONE ON THE DEVELOPMENT, OVIDUCTAL TRANSPORT AND UTERINE RETENTION OF EGGS IN HYPOPHYSECTOMIZED PREGNANT RATS

Abstract

SUMMARY Hypophysectomy of rats on day 1 of pregnancy resulted in expulsion of most eggs from the uterus between days 5 and 6, delayed entry of eggs into the uterus, and retarded development of eggs. Expulsion of eggs was prevented with daily injections of 2 mg progesterone. Other regimes of progesterone administration were also beneficial, but not as effective as daily injections. Daily injections of 2 or 4 mg progesterone, or of progesterone plus oestrone, restored egg transport to normal, whereas a single injection of progesterone did not. Daily injections of small amounts of oestrone caused total disappearance of eggs from the reproductive tract. The development of eggs was significantly improved with daily injections of progesterone plus oestrone, but not with progesterone alone. Combined treatment with progesterone and oestrone caused premature shedding of the zona pellucida in mature blastocysts, young blastocysts, and morulae.