Effects of Progesterone and Oestradiol on RNA and Protein Metabolism in the Genital Tract and on Survival of Embryos in the Ovariectomized Ewe

Abstract

The hormonal regulation of metabolism in the genital tract and the development of embryos during early pregnancy in the ewe have been examined. Ovariectomized ewes received injections of main· tenance progesterone, oestrous oestradiol and priming progesterone according to schedules designed to simulate endogenous ovarian secretion during early pregnancy, around the time of oestrus and during the luteal phase of the oestrous cycle immediately preceding oestrus.The survival and development of embryos was dependent upon the dose of maintenance progesterone and the duration of treatment at the time of transfer, but changes in progesterone dose did not change endometrial protein or RNA metabolism on particular days. Both priming progesterone and oestrous oestradiol were required for normal embryo development. Priming progesterone and oestrous oestradiol each increased endometrial RNA/DNA ratios during early pregnancy. There were no interactions between priming progesterone and oestrous oestradiol, their effects being simply additive. Neither maintenance nor priming progesterone had any effect on protein and RNA metabolism in the oviduct. It is suggested that in the intact ewe oestrogen secreted at oestrus and progesterone secreted prior to oestrus play important roles in the establishment of a uterine environment suitable for the subsequent normal development of embryos.

Oestradiol and Progesterone: Soluble Receptor Levels and Metabolism in the Uterus of the Ovariectomized Ewe

“…that the likely role of oestrous oestradiol is to maintain the sensitivity of the uterus to oestradiol and to progesterone by virtue of its ability to regulate their receptor levels. The role of progesterone secreted during the previous luteal phase is not clear either from the present study or from influences on endometrial metabolism (Miller and Moore 1976) and requires further investigation.…”

“…The support of a high proportion of normal embryos requires the inclusion of all three treatments studied here (Miller and Moore 1976). The present results indicate.…”

“…The treatments and their iI\iection and slaughter schedules have been described in detail (Miller and Moore 1976). Briefly, all animals received an initial injection of oestradiol and were then placed on one of five treatments.…”

“…It is not clear, however, just what influences progesterone secreted during the previous luteal phase and oestradiol secreted to induce oestrus have on this ability of progesterone to maintain early pregnancy. Using a model system in the ovariectomized animal, Miller and Moore (1976) have described the effects of priming progesterone administered prior to oestrus, oestradiol administered to induce oestrus and maintenance progesterone administered subsequent to oestrus, on protein and RNA metabolism in the endometrium and on the ability of the uterus to support transferred embryos. In this paper the levels of soluble oestradiol and progesterone receptors, and oestradiol and progesterone metabolism in uterine tissue in those same animals are described.…”

Establishment and maintenance of pregnancy after embryo transfer in ovariectomized mares treated with progesterone

“…ovariectomized before the oestrus and ovulation associated with pregnancy) may be studied using embryo transfer and hormone replacement therapy. These requirements have been determined for some species, notably the rat (Psychoyos, 1961), mouse (Humphrey, 1969) and ewe (Miller & Moore, 1976).…”