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

Abstract

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