Early Pregnancy in the Ewe: Effects of Oestradiol and Progesterone on Uterine Metabolism and on Embryo Survival

Abstract

The hormonal regulation of embryo development during early pregnancy in the ewe has been examined. Ovariectomized ewes received injections of oestradiol (E2) and progesterone (P) according to schedules designed to simulate endogenous ovarian secretion during the luteal phase of the previous oestrous cycle (priming P), around the time of oestrus (oestrous E2 ) and during early pregnancy (maintenance P, maintenance E2)' Embryos were transferred to the ewes on the 4th day after induced oestrus, and ewes were killed at 6 or 13 days after transfer to assess embryo development. Cytosol concentrations of oestradiol 'and progesterone receptors and RNA and protein metabolism in the endometrium and amounts of protein in uterine flushings were examined on the day of embryo transfer and 6 days after transfer.