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Search for other papers by G. T. Waites in
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Search for other papers by R. F. L. James in
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ABSTRACT
We have previously shown that pregnancy-associated endometrial α1-globulin, a small molecular weight insulin-like growth factor-binding protein (IGF-BP), is quantitatively the major secretory protein product of the decidualized endometrium during human pregnancy. In the present study, employing monoclonal antibodies raised against this protein in an immunohistological technique, the cellular localization of the protein has been examined in the decidua and placenta during pregnancy. During the first trimester the protein was principally associated with the decidual cell in the decidualized decidua compacta region of the endometrium with both cytoplasmic and extracellular matrix-associated staining patterns being detected. No extensive staining was observed in the placenta. At term the protein was localized in similar cells in the placental bed and endometrium associated with the amniochorion but not in the placenta. These studies suggest that the decidual cell represents the major source of IGF-BP during pregnancy and have relevance to the origin of amniotic fluid IGF-BP and the paracrine role of the decidual cell in the control of trophoblast growth.
Journal of Endocrinology (1989) 120, 351–357
Search for other papers by RUTH E. FOWLER in
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Search for other papers by R. G. EDWARDS in
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SUMMARY
1. The injection of 1 i.u. pregnant mares' serum (PMS) followed after 40 hr by 2 i.u. human chorionic gonadotrophin (HCG), or of 3 i.u. PMS followed by 3 i.u. HCG into mature female mice selected at random with regard to their oestrous cycle induces oestrus and mating in approximately 75%, and ovulation in 99% of them.
2. The induction of superovulation depends on the amount of PMS injected and on the strain of mice used.
3. Two types of egg are ovulated, one being normal and with a cumulus, the other degenerated and without cumulus. 93% of the normal eggs were fertilized and 98% of the pronucleate eggs possessed two pronuclei.
4. Approximately three-quarters of the females which mate in response to the injected gonadotrophins become pregnant, although this number was less than the number becoming pregnant after mating during natural oestrus. Many of the treated females carried their embryos to term and some gave birth to large litters, although resorptions, irregular distribution of embryos in the uterus, and difficulty during parturition occurred in some females. Mean litter size of the treated females was similar to that found after natural mating.
5. After more than one treatment with gonadotrophins, fewer females mated, ovulated, and became pregnant than after the first treatment. This reduction in response may have been due to the greater age of the females or to their decreased sensitivity to the hormones.
6. The value of the method as a technique for inducing oestrus, ovulation, and pregnancy in mature female mice is considered.
Search for other papers by M Casais in
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Most of the fibres that constitute the superior ovarian nerve (SON) originate at the neuronal bodies of the coeliac ganglion and innervate rat ovarian stroma cells. The purpose of this work was to study the part played by innervation on ovarian release of progesterone on day 15 and at the end of pregnancy in an integrated in vitro system known as the coeliac ganglion-SON-ovary system. We also investigated, in the same system, whether there is some kind of inter-relationship between the effect of adrenergic agents and LH on progesterone release on day 15 of pregnancy. The coeliac ganglion and the ovary were incubated in separate compartments, linked by the SON. The ovary was immersed in 2 ml buffer solution (ovarian compartment) and the coeliac ganglion was immersed in 2 ml of a different buffer solution (ganglion compartment). Under these conditions, the accumulation of progesterone in the ovarian compartment medium was used as an endpoint. Conditions were standardised on day 15 of pregnancy, when the decrease in the release of ovarian progesterone caused by non-specific stimulation on the ganglion with KCl (56 mM) demonstrated the functional integrity of the system. Neural influence was evaluated by the addition of adrenergic agents at a concentration of 10(-6)M to the coeliac ganglion. On day 15 of pregnancy, noradrenaline and propranolol increased progesterone release while phentolamine diminished it. The existence of ganglionic tone was assessed by analysing progesterone basal levels at different stages of pregnancy. The highest secretion of progesterone was found to take place on day 15, diminishing as pregnancy advanced. In addition, adrenergic neural participation was studied during the physiological luteolysis occurring at the end of pregnancy. Major findings were that noradrenaline increased ovarian accumulation of progesterone on day 19 and decreased it on day 20, while propranolol and phentolamine diminished progesterone release on both days. In additional studies, some neuroendocrine aspects were investigated at a peripheral level. The addition of LH only to the ovarian compartment did not affect progesterone secretion. However, when LH in the ovarian compartment was accompanied by noradrenaline, propranolol or phentolamine in the ganglion compartment, the release of progesterone decreased. It can be concluded that modifications of the neural state of the coeliac ganglion affect ovarian progesterone secretion and the physiology of pregnancy via the SON. The results may confirm that the coeliac ganglion-SON-ovary system provides a direct link between the autonomic nervous system and physiological events during pregnancy.
Search for other papers by S. J. Arkinstall in
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Search for other papers by C. T. Jones in
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ABSTRACT
The regulatory factors controlling uterine activity during pregnancy remain unclear in many species. Since myometrial relaxants raise intracellular cyclic AMP, modulation of signalling pathways coupling cell-surface receptors to adenylate cyclase activation could be an important site for control. To assess the functional activity of the stimulatory GTP-binding protein Gs we have measured adenylate cyclase activation by GTP, its non-hydrolysable analogue guanosine 5′-(β-γ-imido)triphosphate (Gpp(NH)p), fluoride, forskolin and manganese in a 50 000 g membrane fraction prepared from the myometrium of non-pregnant, mid-pregnant (30–32 days) and late-pregnant (62–66 days) guinea-pigs (full term 67±2 days). While forskolin- and manganese-dependent enzyme activation was unaltered by pregnancy, maximal stimulation by Gpp(NH)p and fluoride was enhanced by up to 200%. Recovery of adenylate cyclase activity in the 50 000 g fraction was essentially constant at 20–24% of the total activity throughout pregnancy, and thus cannot explain the increases observed. Since guanine nucleotides and fluoride stimulate adenylate cyclase through activating Gs, and forskolin and manganese act at the level of the catalytic unit, these data are consistent with a pregnancy-related increase in Gs functional coupling while adenylate cyclase activity is unaltered. These observations suggest a physiological regulation of myometrial Gs activity during pregnancy which could facilitate hormonal stimulation of adenylate cyclase and contribute to uterine quiescence by increasing uterine sensitivity to relaxants.
Journal of Endocrinology (1990) 127, 15–21
Search for other papers by M Davenport in
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Search for other papers by J L Morton in
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Search for other papers by M A Cawthorne in
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Abstract
The mechanisms which initiate and maintain the energy partitioning into maternal tissues during pregnancy are unknown. The present study shows that in each of the weeks prior to pregnancy in the rat, plasma β-cell tropin (βCT) concentrations (nmol/l) were 0·68±0·10, 0·61 ±0·14 and 0·73±0·11 (n=11, mean±s.e.m.). During early (1-3 days) pregnancy the concentration rose to 1·32 ±0·26 and by early-mid (7–10 days) pregnancy they had increased to 1·96 ±0·41. By mid-late (14–17 days) pregnancy plasma βCT concentration had declined to the prepregnancy concentrations (0·67 ± 0·16). This mid-term increase in the circultating concentration of the lipogenic hormone βCT may contribute to the deposition of lipid associated with the early period of gestation. The increased circulating βCT could be derived from the pituitary gland neurointermediate lobe or by secretion from the placenta. It should be emphasised that the measurements in the present study represent a 'snap-shot' at discrete intervals and do not provide information about the dynamic hormonal interplay which occurs physiologically.
Journal of Endocrinology (1995) 146, 177–182
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ABSTRACT
We have previously demonstrated insulin resistance in the liver and peripheral tissues of the adult offspring of rats made diabetic with streptozotocin (SDF rats). In this study, a euglycaemic hyperinsulinaemic clamp was used to test the hypothesis that insulin resistance is further aggravated during pregnancy in SDF rats. Normal pregnancy was accompanied by a decrease in the sensitivity of the liver and peripheral tissues to insulin, with a normal responsiveness to insulin. In SDF rats no further decrease in the sensitivity of peripheral tissues to insulin occurred during pregnancy when compared with non-pregnant rats, and the dose–response curves of the glucose metabolic clearance rate during hyperinsulinaemia were similar in pregnant control and pregnant SDF rats. There was, however, a modest decrease in the sensitivity of the liver to insulin during pregnancy in SDF rats.
The normal increase in plasma insulin levels during pregnancy was blunted in SDF rats: this resulted in increased glucose levels in maternal and fetal rats and increased fetal insulin concentrations, features compatible with mild 'gestational diabetes'.
In conclusion, gestational diabetes develops in pregnant SDF rats, although there is no further deterioration in peripheral insulin resistance.
Journal of Endocrinology (1991) 131, 387–393
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Search for other papers by E. A. MICHIE in
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Search for other papers by R. VIHKO in
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SUMMARY
Steroid disulphate fractions were obtained by chromatography on Sephadex LH-20 from samples of amniotic fluid from three pregnancies complicated by anencephaly. Several of the steroids with a 3β-hydroxy-5-ene structure found in normal amniotic fluid could not be detected. 5-Androstene-3β,17α-diol, the main steroid disulphate in normal amniotic fluid was present in concentrations of <5% of the values at normal term. The disulphates of neutral steroids found in highest concentrations in the amniotic fluid of anencephalic pregnancies were those of isomeric pregnanediols; 5α-pregnane-3α,20α-diol, 5α-pregnane-3β,20α-diol and 5β-pregnane-3α,20α-diol. The quantities of these metabolites of progesterone in the amniotic fluid of anencephalic pregnancies were similar to those in normal pregnancies. A saturated 18-hydroxylated C19 steroid, most probably 3α,18-dihydroxy-5α-androstan-17-one, was identified by gas—liquid chromatography and gas chromatography—mass spectrometry. Although this compound has been previously identified in human bile and in normal pregnancy urine, this appears to be the first identification of a saturated C19 steroid in amniotic fluid.
Search for other papers by DIANE M. RIMMER in
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SUMMARY
The collagen content of the cervix of the pregnant mouse was found to be least on day 10 of pregnancy and greatest just before parturition (day 19). Similarly, the weight of cervical tissue was least on day 9 and greatest at parturition (day 20). However, the collagen concentration in the tissue was maximal on day 9 (7·54% of wet weight) and minimal on day 20 (1·56% of wet weight) because the collagen content decreased more than the weight during the first half of pregnancy and the weight increased more than the collagen during the latter part of pregnancy. Fluctuations in the trend of results were recorded early in the second half of pregnancy and steady changes were only observed in the last few days before parturition. On the first day post partum, conditions had returned to the oestrous state. The results are discussed with regard to the endocrine state of the animal and comparisons are made with changes in the rat cervix during pregnancy.
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ABSTRACT
Plasma concentrations of atrial natriuretic peptides (ANP) in female Wistar rats were measured by radioimmunoassay at oestrus, during pregnancy, during parturition and between 3 h and 4 days post partum. Concentrations of ANP in rats on days 10, 15 and 17 of pregnancy were not significantly different from those in non-pregnant animals in oestrus (32·5 ± 2·2 pmol/l; mean ± s.e.m., n = 9), but levels near term (days 20 and 21 of pregnancy) were reduced by approximately 50%. However, plasma concentrations of ANP at 6, 12 and 24 h post partum were approximately twice those of non-pregnant animals in oestrus, but returned to normal levels within 4 days after parturition. Maternal plasma volume increased significantly during pregnancy, and fell 15–20% 6–24 h post partum. These results suggest that the relationship between plasma volume and the plasma concentration of ANP is reset during pregnancy and changes rapidly post partum. The results do not necessarily, however, imply any changes in the relationship between atrial pressure and the concentration of ANP.
Journal of Endocrinology (1989) 120, 113–117
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The aim of this study was to examine the changes in collagen metabolism that occur during pregnancy and parturition and upon relaxin administration to the rat pubic symphysial interpubic tissue. Pubic symphyses were collected from non-pregnant, and intact and ovariectomised pregnant Sprague-Dawley rats at days 15, 18 and 21 of pregnancy as well as during and after delivery, and analysed for collagen content and solubility. SDS-PAGE was used to determine collagen composition. During pregnancy and particularly during birth, there was a significant reduction in both the tissue wet (57+/-3%) and dry (43+/-3%) weight (n=7), which coincided with a significant increase in water content (to 80%) and was attributed to a significant (P<0.05) reduction in overall tissue collagen content (by 47+/-2%). This resulted in both soluble (10%) and insoluble (90%) collagen levels being reduced, but gel electrophoresis demonstrated the presence of types I, II and V collagen in all samples. Western blot analysis confirmed the presence of type II collagen throughout pregnancy, confirming that the rat pubic symphysis remained a fibrocartilaginous tissue throughout gestation. In the absence of the ovaries and hence relaxin, tissue collagen content and solubility were not significantly different from control measurements. However, tissues of ovariectomised animals treated with oestrogen and progesterone (pellets) and relaxin (injection) contained collagen levels that mimicked those of late pregnancy and parturition. These results suggest that relaxin plays an important role in regulating collagen catabolism during gestation in the rat.
