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Search for other papers by AG Gunin in
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The aim of this study was to examine the role of heparin in the realization of oestradiol (OE2) effects in the uterus. Ovariectomized rats were treated with a single injection of OE2 dipropionate (10 micrograms/rat, i.m.) along with injections of heparin (in doses of 0.4 mg/rat, i.m.). OE2 effects in the uterus were determined by measuring mitotic indices, proliferating cell nuclear antigen (PCNA)-labelling indices, DNA content, and volumes of cells, nuclei and nucleoli in luminal and glandular epithelia and stromal cells of the endometrium 24, 36 and 48 h after the injection of OE2. Heparin treatment inhibited the OE2-stimulated increase in mitotic activity and DNA content of the uterine structures, whereas OE2-induced increases in cell, nucleus and nucleolus volumes in all uterine structures tested at all the times were greatly augmented by heparin. The OE2-induced increase in PCNA-labelling index in all the cell types had a tendency to increase as the result of heparin action. In the absence of OE2, heparin had no effect on any of the uterine parameters. The effect of heparin is probably realized via changes in the mechanism of oestrogen action in the uterus. Heparin probably prevents passage of the cells from the G1- to the S-phase of the cell cycle and prolongation of the G1-phase with consequent accumulation of the cells in this phase of the cell cycle. This probably leads to reduction of mitotic activity. Furthermore, cells in G1-phase probably prolong their biosynthetic processes causing enlargement of the cell, nucleus and nucleolus volumes.
Search for other papers by F. H. BRONSON in
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Search for other papers by T. H. HAMILTON in
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SUMMARY
Two experiments were performed to examine variations in whole-organ concentrations of RNA, DNA and protein, and specific activities of RNA in vivo in the mouse oviduct and uterus during the oestrous cycle and early pregnancy. Concentrations of DNA did not vary in the oviduct at any stage of the reproductive cycle in either study. In the first experiment with Yale Swiss mice, the concentration of RNA in the oviduct was highest at pro-oestrus, somewhat lower at mid-day of oestrus, and lowest on days 2, 4 and 12 after insemination. Concentrations of RNA were essentially identical in the oviducts of inseminated and non-inseminated females at mid-day of the day following ovulation. The second experiment, using CF-1 mice, confirmed these results, and, in addition, examined oviducal and uterine uptake and incorporation of [3H]uridine. Incorporation of the radioactive precursor into RNA was highest in the oviduct at mid-day of pro-oestrus, was markedly decreased before ovulation, and remained relatively low during the period of egg transport in both inseminated and non-inseminated mice. Most of the RNA necessary for appropriate oviducal function during zygote transport, therefore, is synthesized well before ovulation, and relatively little is formed during the 3 days of tubal residence. The general pattern of incorporation of [3H]uridine into RNA in the uterus appeared basically similar to that shown by the oviduct, except at mid-pregnancy when transcriptional activity of the oviduct genome was relatively low. The two organs also differed markedly in the magnitude of the pro-oestrous surge in RNA synthesis and accumulation, with the uterus showing a greater increase.
Search for other papers by CK Ho in
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Search for other papers by SG Hillier in
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Glucocorticoids are known to have diverse effects on the uterus, generally believed to be mediated by the glucocorticoid receptor (GR). To date, two isoforms of the enzyme 11beta-hydroxysteroid dehydrogenase (11betaHSD) have been identified, namely 11betaHSD1 and 11betaHSD2, which interconvert active and inactive glucocorticoids and regulate local levels of hormones available to the GR in target tissues. The aim of the present study was to examine the uterine expression of 11betaHSD and GR mRNA. The interplay of these parameters is probably an important factor in determining actions of glucocorticoids on the uterus. Using Northern analysis we investigated the uterine expression of 11betaHSD1, 11betaHSD2 and GR mRNA in relation to serum levels of sex steroid hormones and uterine progesterone receptor mRNA expression in an animal model. Immature female rats were treated with 10 IU pregnant mare serum gonadotrophin (PMSG) followed by 10 IU human chorionic gonadotrophin (hCG) 48 h afterwards, and then killed at 0, 3, 6, 9, 12 and 24 h and 5 days after the hCG injection. Expression of both 11betaHSD1 and 11betaHSD2 mRNA in total uterine RNA was found to be up-regulated by more than 50% at 48 h after PMSG injection when oestradiol levels were also high. Following hCG treatment the expression of 11betaHSD1 and 11betaHSD2 further increased to reach maximal levels at 24 and 12 h respectively. GR mRNA expression was down-regulated by more than 50% by PMSG but gradually recovered after hCG injection. The results show that mRNA expression of 11betaHSD1, 11betaHSD2 and GR in the uterus is developmentally regulated, suggesting that these key determinants of glucocorticoid action may play an important role in uterine function.
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Several regulatory enzymes of carbohydrate metabolism were studied in blastocysts and uteri of mice in which implantation had been delayed and of oestrogen-activated mice, and compared with those of normal mice just before implantation on day 4 of pregnancy. A significant increase in the activities of phosphofructokinase and pyruvate kinase was observed but the level of lactate dehydrogenase declined in delayed blastocysts. Carbohydrate metabolism in the uterus remained essentially unchanged during the delay period. A study of uterine mitotic patterns showed a steady increase in stromal mitosis after administration of oestradiol to animals in which implantation had been delayed.
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An attempt has been made to assess quantitatively the extent of cell death in the uterine epithelium after oestrogen treatment. [3H]Thymidine was injected into ovariectomized mice at an interval after oestrogen treatment when many of the luminal epithelial cells were in the S phase of mitosis. Uptake of [3H]thymidine was confirmed by autoradiography of sections of uterus and scintillation counting of trichloracetic acid-insoluble fraction of whole uterine horns. Radioactivity declined after the cessation of oestrogen treatment but remained high if treatment was continued. The decline appears to be correlated with the cell death previously demonstrated in histological sections of uteri under similar conditions.
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ABSTRACT
Plasma concentrations of FSH and LH were measured in ovariectomized, ovohysterectomized, hysterectomized and sham-operated adult, non-pregnant rats at 3, 14, 21 and 28 days after operation. From day 21 after the operation onwards, there were higher concentrations of FSH in plasma in ovohysterectomized than in ovariectomized animals. The concentration of LH was not influenced by hysterectomy. The inhibitory response of FSH and LH to a single dose of oestradiol was not altered by any of the operations. By 2 weeks after surgery, pituitary FSH content had increased in ovohysterectomized animals compared with ovariectomized ones, but this difference was eliminated when ovohysterectomized animals were treated with crude uterine extract. Pituitary contents of LH and prolactin were not influenced by hysterectomy or by treatment with uterine extract, thus indicating the specificity of an inhibitory effect of the uterus on FSH levels. Treatment of hysterectomized and intact animals with uterine extract resulted in a reduction in the weight of the ovaries of 23–38% (P<0·05), indirectly showing the presence of an FSH-inhibiting substance in the extract.
Fractionated uterine extract inhibited FSH synthesis by rat pituitary cells in vitro, but had no effect on LH synthesis. Chromatographic analysis indicated that the FSH-inhibiting substance in the uterus has a molecular weight of 10 000–20 000.
Journal of Endocrinology (1990) 124, 183–189
Search for other papers by B. G. MILLER in
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SUMMARY
Changes in the metabolism of pyrimidine 5′-nucleotides and RNA in the mouse uterus during the oil-induced decidual cell reaction were investigated. During the first 20 h after the intraluminal injection of 10 μl sesame oil the amounts of HClO4-soluble nucleotides and uridine 5′-nucleotides in the treated horn increased by 55% and 115%, respectively. During the same interval RNA increased by 101%, while the increase in protein was much smaller, and the amount of DNA remained almost unchanged.
Doses of [2-14C]uridine, [5-3H]cytidine and [5-3H]orotic acid were administered to mice 20 min before killing. After [2-14C]uridine injection the specific activity of the uridine 5′-nucleotide fraction 20 h after the oil stimulus had not changed, while the specific activity of RNA increased by 43% during the 20-h interval. Similar results were obtained when [5-3H]-cytidine was injected. In contrast, after an injection of [5-3H]orotic acid the specific activities of both the uridine 5′-nucleotide and RNA fractions decreased with increasing time after the intraluminal injection of oil. When approximate rates of RNA synthesis were calculated independently from the data for [2-14C]uridine and [5-3H]orotic acid incorporation in these two fractions, the results agreed well, and indicated that the rate of synthesis of RNA in the decidualizing uterus increased by 64% and 163% at 8 and 20 h respectively after the intraluminal administration of sesame oil.
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Search for other papers by P. J. HEALD in
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SUMMARY
Measurement of the uptake and retention of a radioactive post-coital antifertility agent tamoxifen, by reproductive tissues of the rat have shown that the ovary retained more radioactivity than did any other reproductive organ. Studies have also been made of the uptake and distribution of [3H]tamoxifen and [3H]oestradiol-17β in the uterus of the pregnant rat on days 2–6 post coitum. Twenty-four hours after administration of tamoxifen, either i.v. or orally, 40–50% of the radioactivity was in the high speed pellet, 10–20% in the nuclear fraction, and 15–30% in the cytosol. An equivalent dose of [3H]oestradiol-17β yielded distributions of 5%, 5% and 82% respectively. Fractionation of uteri from animals given 0·2 mg tamoxifen/kg on Day 2 of pregnancy followed by [3H]oestradiol 60 min before death showed little difference in total uptake of oestradiol or distribution in the subcellular fraction on Days 4, 5 and 6. Although uptake of oestradiol by uterine nuclei was reduced on Day 3 by previous administration of tamoxifen on Day 2, appreciable quantities were still bound to the nuclear receptors. Treatment of ovariectomized animals with tamoxifen at doses up to 40 μg/rat (i.e. 0·2 mg/kg) led to the accumulation of oestrogen–receptor complex in the nucleus.
It is concluded that the antifertility properties of tamoxifen (under the conditions of these experiments) cannot be ascribed to the suppression of uptake and binding of oestradiol by the uterus.
Search for other papers by ANNE McLAREN in
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SUMMARY
The effects of ovariectomy at different stages of early pregnancy, and the response to various amounts of exogenous progesterone and oestrogen, were studied in Q-strain mice. When the ovaries were removed on the third day of pregnancy, unimplanted blastocysts were retained in the uterus and no lysis of the zona pellucida occurred; removal on the following morning permitted lysis of the zona pellucida but again no implantation; by the afternoon the ovaries were no longer required for the initiation of implantation, but in the absence of progesterone no sites were maintained. A single dose of oestrogen eliminated all unimplanted blastocysts from the uteri of ovariectomized mice. Daily treatment with a low dose of progesterone after ovariectomy on the third day altered the appearance of the uterus but did not permit implantation unless oestrogen was also given. Under all the above conditions, some reduction in the number of embryos occurred. The maximum number of implantation sites in ovariectomized mice was achieved by daily injection of a high dose of progesterone, with no added oestrogen. An intermediate level of progesterone induced abortive implantation in mice ovariectomized on the third day, and abnormal development of implantation sites after ovariectomy on the fourth day. When the start of progesterone injections was postponed, either after ovariectomy or during lactational delay, it proved more difficult to induce implantation with the progesterone preparation alone, in the absence of added oestrogen.
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Search for other papers by F. G. SULMAN in
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SUMMARY
Radioactive [14C]5-hydroxytryptamine (5-HT, serotonin) creatinine sulphate was injected intrapleurally into female rats treated with oestrogen and/or progesterone which had received, immediately before the injection of 5-HT, homogenates of placenta, foetus, uterus or plasma, taken from pregnant rats on the 19th day of pregnancy. The placental homogenate produced a significant increase in 5-HT uptake by the myometrium, when the rats had been primed with moderate doses of oestrogen plus progesterone. Higher doses prevented the increased uptake, and oestrogen treatment alone did not induce 5-HT uptake. The highest level of 5-HT accumulation in the uterus was produced by placental extract after pretreatment with 0·5 mg. oestradiol plus 10 mg. progesterone/rat/day.
These results suggest that the placenta contains a 'trans-serotonin' system which is dependent on the oestrogen—progesterone balance and serves to accumulate 5-HT in the placenta and myometrium. Shifts of the hormonal balance may contribute to the release of 5-HT and thus promote uterine contractions at any stage of pregnancy.
