The Maintenance of Early Pregnancy in the Ovariectomized Ewe by Injection of Ovarian Hormones

Ovariectomized ewes received injections designed to mimic to some extent oestradiol and progesterone secretion during early pregnancy (maintenance progesterone), during oestrus (oestrous oestradiol) and during the luteal phase of the previous cycle (priming progesterone). The animals were killed at times equivalent to 1, 4 or 7 days after oestrus in those animals which had received oestrous oestradiol. The level of soluble oestradiol and progesterone receptors in whole uterus, and [3Hloestradiol and [3Hlprogesterone metabolism by uterus minces were measured.Oestradiol receptor level was highest on day 1 in those animals receiving oestrous oestradiol with no significant effect at any stage of the inclusion or omission of priming or maintenance progesterone. Progesterone receptor level was also high on day 1 in those animals receiving oestrous oestradiol with high levels maintained to day 4. Again, inclusion of priming or maintenance progesterone was without effect. In animals not receiving oestrous oestradiol the level of both receptors was uniformly low.Metabolism of [3Hloestradiol was low and not affected by treatment. [3HIProgesterone metabolism, although more variable, was also low and not affected by treatment.

Section: Introductionmentioning

confidence: 96%

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

Murphy¹,

Stone²,

Miller³

et al. 1977

“…In the ewe it has been shown in animals ovariectomized a few days after mating that progesterone will maintain early pregnancy (Foote et al 1957;Moore and Rowson 1959;Bindon 1971;Cumming et al 1974;Trounson and Moore 1974). However, prior to ovariectomy the ewe would have been under the influence of oestrogen secreted around the time of oestrus, and of progesterone secreted during the luteal phase of the oestrous cycle immediately preceding oestrus.…”

Section: Introductionmentioning

confidence: 99%

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

Miller¹,

Moore²

1976

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.

“…It is known that when ovariectomy is performed on day 20, pregnancy can be maintained in the ewe by injections of progesterone until the placenta assumes this role around day 50 (Neher and Zarrow 1954;Moore and Rowson 1959;Alexander and Williams 1966). There are two reports where ovariectomy was performed during the first few days of pregnancy and the ewes treated from this time with mixtures of progesterone and oestradiol (Foote et al 1957;Moore 1963). It appeared from these that progesterone alone was sufficient for implantation and normal embryo development.…”

Section: Introductionmentioning

confidence: 99%

The Role of Progesterone in Implantation in the Sheep

Bm¹

1971

SummaryMerino ewes were ovariectomized on days 4, 8, or 12 of pregnancy and injected daily from that time with 1, 4, or 16 mg progesterone in oil. The ewes were killed on day 20 and examined for embryos. There was a clear effect of dose of progesterone on the number and viability of embryos. Of the ewes receiving 1, 4, and 16 mg progesterone there were 0 out of 12, 2 out of 11, and 11 out of 14 with viable embryos on day 20. The effect of increasing progesterone was also seen in significantly increased glandular and luminal epithelial cell heights in ewes receiving 16 mg per day.Plasma progesterone was measured daily during days 1-5 and twice daily during days 6-15 of pregnancy and of the oestrous cycle. The numbers of corpora lutea and embryos in these animals were verified at laparotomy on days 15-18. The difference between pregnant and non-pregnant ewes with regard to plasma progesterone was not significant until days 16-17. Both pregnant and non-pregnant ewes had highest levels of progesterone during the period day 10 to day 14. Different ewes had peak values at different times so that the mean progesterone values took the form of a variable plateau, lasting several days, of 2-3 ng/ml.Peak levels of progesterone appeared in the plasma at times consistent with the idea that this hormone is responsible for the rapid preimplantation growth phase of the embryo during days 11-15.