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ABSTRACT
Induction of ovulation early post partum in sheep is associated with a high incidence (30–40%) of premature luteolysis. The present study was designed to characterize oxytocin receptor levels, oxytocin-stimulated inositol phosphate (IP) turnover (second messenger) and oxytocin-stimulated prostaglandin F2α (PGF2α) release in the endometrium of post-partum ewes induced to ovulate 21 days after parturition and expected to exhibit a range of corpus luteal functions subsequently.
Ovulation was induced on day 21 post partum using a controlled internal drug release device and pregnant mare serum gonadotrophin, and uterine tissues were collected on days 5, 10 or 15 of the cycle (n = 4/day). A further 12 ewes whose interval from previous parturition exceeded 150 days were similarly treated and acted as controls. Measurement of daily peripheral progesterone concentrations revealed that while all control ewes exhibited normal luteal function, abnormal luteal function was evident in two, two and one post-partum ewes studied on days 5, 10 and 15 of the cycle respectively. Oxytocin receptor binding was detected (by receptor-binding assay and in-vitro autoradiography) in the endometrium and myometrium of post-partum ewes at all three stages of the oestrous cycle but only at day 15 in control ewes. To determine IP turnover, 100 mg caruncular endometrium was incubated in duplicate for 2·5 h with 10 μCi [3H]inositol and treated with 0 or 2 μmol oxytocin/l for 30 min, then [3H]inositol mono-, bis- and trisphosphates were quantified. Oxytocin stimulated total IPs in all day-5 and day-15 post-partum ewes, in three of four day-10 ewes and in all day-15 control ewes. Basal endometrial PGF2α release measured in triplicate (100 mg/well) during a 2 h incubation was higher in post-partum versus control ewes on days 5 and 10 but not on day 15 of the cycle. Similarly, oxytocin stimulated PGF2α release to varying levels at all stages of the cycle in post-partum ewes but only on day 15 in control ewes. Irrespective of the treatment group endometrial oxytocin receptor number was significantly (P < 0·001) correlated with oxytocin-stimulated IP turnover and PGF2α release.
Thus the induction of ovulation and the subsequent luteal phase in post-partum ewes is against a back ground of high oxytocin receptor expression and enhanced PGF2α release which in some ewes may contribute to abnormal luteal function.
Journal of Endocrinology (1993) 136, 17–25
Search for other papers by S. NORDQVIST in
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SUMMARY
A method is described for short-term incubations in vitro of normal endometrium for the study of nucleic acid synthesis. Tissue suspensions of specimens obtained at curettage were incubated with and without hormones in a medium consisting of Parker's 199 medium and 20% adult human serum; [3H]thymidine and [14C]uridine were added. The isotope uptake into the nucleic acids was determined and related to the total amount of DNA in each sample. Marked variation in DNA synthesis was noted in endometria obtained at different phases of the menstrual cycle. RNA synthesis varied less. After the addition of progesterone, synthesis of both nucleic acids was reduced. The magnitude of this response varied in different endometria. Thus DNA synthesis in endometria already under strong progesterone influence in vivo (midsecretory phase) was least affected when progesterone was added in vitro.
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ABSTRACT
Ovariectomized mice were prepared for decidualization with oestrogen and progesterone and arachis oil injected into the uterine lumen. Hormone injections were then stopped and uteri examined at intervals between 31 and 84 h after the last progesterone injection. At 31 and 35 h the stroma showed a normal decidual reaction. Between 45 and 79 h the stroma underwent a series of changes which started with the congestion of dilated blood vessels with swollen erythrocytes followed by breakdown of the vessel walls and extravasation of blood. At the same time the decidual cells showed typical apoptotic changes and there was invasion by leucocytes. An outer ring of stroma did not take part in the degenerative process and eventually a central core of blood cells and degenerating decidual cells became detached and was shed into the lumen.
Animals treated in exactly the same way but with the omission of the decidual stimulus did not show such changes in the stroma. It is suggested that the changes in the endometrium resemble those of menstruation and support the suggestion that for menstruation to occur the stroma must be differentiated for implantation. This occurs during the cycle in women but does not occur in non-primates unless a decidual stimulus is applied to the uterus.
J. Endocr. (1984) 100, 295–300
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A single, low-dose administration of a potent antiprogesterone such as mifepristone (RU486) in the early luteal phase results in inhibition of blastocyst implantation in primates. The aim of the present study was to examine the status of leukaemia inhibitory factor (LIF), transforming growth factor beta (TGF beta) and vascular endothelial growth factor (VEGF) in day 6 gestational endometrium of rhesus monkeys with or without exposure to a single dose (2 mg/kg body weight, s.c.) of mifepristone on day 2 after ovulation. Densitometric analyses of immunoblots of endometrial spent media revealed an increase (P < 0.01) in TGF beta pan (TGF beta 1, 2, 3 and 5) and a decrease (P < 0.01) in VEGF secretion from RU486-exposed endometrial samples compared with control samples. Secretory profiles for LIF, TGF beta 1 and TGF beta 1 LAP (latency associated peptide) remained unchanged in the two treatment groups. Morphometric analyses of immunohistochemical staining showed altered cell-specific distribution. TGF beta 1 (P < 0.01) and TGF beta pan (P < 0.02) were higher, while VEGF declined (P < 0.05) in endometrial glands of RU486-exposed endometria compared with control tissue samples. Stromal cell staining patterns for all experimental cytokines studied remained unchanged. In blood vessels, VEGF was found to be low (P < 0.05), while LIF (P < 0.05) and TGF beta 1 (P < 0.01) were higher in mifepristone-exposed endometrial samples compared with control tissue samples. Increased TGF beta secretion together with elevated levels of TGF beta in glandular epithelia and in blood vessels with no apparent change in stromal levels of TGF beta or in levels of TGF beta LAP in any endometrial compartment in the two treatment groups suggest an altered paracrine involvement of this cytokine and an enhanced activation of latent TGF beta in endometrium following mifepristone treatment. Higher levels of TGF beta in gland cells may result in dysregulated growth control and degenerative morphology. Also, higher levels of LIF and TGF beta together with lower levels of VEGF in the vascular compartment in mifepristone-exposed endometrium suggest that endometrial vascular physiology is a target of this anti-progestin during the peri-implantation stage. It is thus plausible that LIF, TGF beta and VEGF in the glandular and vascular compartments of implantation stage endometrium play important roles in rendering the endometrium receptive, and that early luteal phase treatment with an anti-progestin such as mifepristone affects the involvement of these cytokines resulting in endometrial contraception.
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The concentrations of prostaglandins F2α (PGF) and E2 (PGE) were measured by gas chromatography–mass spectrometry in endometrial tissue obtained from 45 normal women at various stages of the menstrual cycle. During the proliferative stages, the concentration of PGF in the endometrium was correlated with the concentration of oestradiol in the plasma. The concentration of PGF during the mid-secretory stage (mean, 2·047, range, 0·549–4·344 μg/g fresh endometrial tissue) was significantly higher than the concentrations during the late proliferative and late secretory stages. The endometrial concentration of PGE did not show a cyclic variation.
The concentrations of PGF and PGE in samples of endometrium collected after the administration of clomiphene were significantly lower than the concentrations observed in endometrial tissue obtained from normally menstruating women in the mid-proliferative period. The administration of an oestrogen–progestogen pill resulted in higher endometrial concentrations of PGE than were measured in the mid-secretory phase. The concentrations of PGF and PGE in decidual tissue (conceptual age 3–10 weeks) were lower than those measured at any stage of the normal menstrual cycle. During the human menstrual cycle, high levels of oestradiol and progesterone are related to high endometrial levels of PGF but not PGE. The presence of a conceptus apparently blocks the effect of high concentrations of ovarian steroids on the synthesis or catabolism of prostaglandins.
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SUMMARY
Human proliferative endometrial tissue was maintained in organ culture. Glandular cells in the fragments were stimulated to secrete by adding progesterone to the culture medium—but not by insulin, oestradiol or cortisol; insulin enhanced the effect of progesterone. With progesterone, subnuclear vacuolation appeared in the glandular cells after 2–3 days. As the culture continued, these vacuoles disappeared and secretion into the lumen occurred.
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SUMMARY
[3H]Thymidine autoradiography was used to study DNA synthesis in the uteri of spayed mice treated with progesterone and oestradiol. Progesterone suppressed DNA synthesis in the glandular epithelium whether oestrogen was given or not. It also suppressed DNA synthesis in the luminal epithelium. Here oestradiol produced morphological changes and eventual re-entry of some cells into DNA synthesis.
Progesterone altered the nuclear morphology of the stromal cells and increased the number synthesizing DNA. In these conditions a single injection of oestrogen was followed 10–15 h later by the synchronized entry into DNA synthesis of 30–40% of stromal cells. However, a second injection produced no further response.
It was concluded that progesterone stimulated stromal cells in the resting phase to enter the cell cycle and that oestrogen then accelerated their passage through a single round of replication and division by shortening the interval between mitosis and DNA synthesis, following which the cells withdrew from the cell cycle.
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Urocortin is a 40-amino acid peptide belonging to the corticotropin-releasing factor (CRF) family. In human reproductive tissues, urocortin expression has been previously demonstrated in the ovary, in the placenta and fetal membranes and in pregnant uterine tissues, while no data are available on the expression of the peptide in the nonpregnant uterus. In this study, urocortin expression was evaluated by both immunohistochemistry and reverse transcription-polymerase chain reaction, in human uterine tissues and cells at different phases of the menstrual cycle. Urocortin was immunolocalized in endometrial epithelial and stromal cells, as well as in the myometrium, and in vascular smooth muscle cells. No differences between proliferative and secretory phase were observed. These results were confirmed by reverse transcription-polymerase chain reaction analysis of isolated endometrial epithelial and stromal cells, and myometrial specimens. These findings open new questions on the roles played by urocortin in the human uterus.
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SUMMARY
Actinomycin D can induce a small number of implantations in pregnant mice undergoing progestin-induced delayed implantation following ovariectomy. However, the response of the uterus to the blastocyst is considerably retarded compared with the response observed when implantation is precipitated by oestradiol.
With the electron microscope the attachment reaction between the trophoblast and uterine epithelium is evident about 48 h after administration of the drug. However, the differentiation of the luminal surface of the epithelial cells in areas of uterus distant from a blastocyst (2nd stage of closure), which normally accompanies implantation, and can be induced by oestradiol in progesterone-treated animals, is not seen. Thus actinomycin D, although allowing implantation to proceed, does not completely mimic the actions of oestradiol on the progesterone-treated uterus.
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Department of Veterinary Anatomy, University of Bristol, Bristol, BS1 5LS
(Received 22 May 1974)
Hydroxysteroid dehydrogenases (HSD's) acting at the 3α, 3β and 16β positions have been demonstrated histochemically in the trophoblast of the established placenta of the pig and 17β-HSD has been identified in the maternal placental epithelium (Christie, 1968; Dufour & Raeside, 1969). This 17β-HSD is also found in the uterine epithelium of the interlocular and unoccupied parts of the pregnant uterus but is absent from the non-pregnant uterus (Flood, unpublished). The object of the present study was to determine the time of appearance of these enzymes.
Eight gilts and one sow were killed at 10, 12(2), 13(2), 14, 15, 16 and 19 days of gestation. The day after first service was regarded as day 0. The uteri were removed within 10 min of slaughter and in the case of the gilt killed at 10 days' gestation, ten
