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ABSTRACT
Maternal plasma concentrations of immunoreactive endothelin (ir-ET) during pregnancy, labour and after birth were measured by radioimmunoassay. Concentrations of ir-ET in the umbilical artery, umbilical vein, amniotic fluid and neonatal urine were also examined.
The mean (± s.e.m.) plasma ir-ET concentration in early pregnancy (4–7 weeks) was 13·7±0·5 pmol/l, which was significantly higher than that in non-pregnant women (5·9±0·3 pmol/l). During pregnancy, plasma ir-ET concentrations gradually decreased to a minimum of 11·5±0·4 pmol/l in weeks 20–23, and then increased again towards term (12·5±0·4 pmol/l after 36 weeks of pregnancy). In women undergoing vaginal delivery, the mean plasma ir-ET concentration (17·1±0·7 pmol/l) increased significantly, compared with that in late pregnancy. After delivery, the plasma ir-ET concentration decreased abruptly to 4·0±0·2 pmol/l on the first day.
Plasma ir-ET concentrations in umbilical vessels were significantly higher than those in maternal plasma. In addition, concentrations in the umbilical artery were significantly higher than those in the umbilical vein in cases of vaginal delivery.
Concentrations of ir-ET in amniotic fluid were much higher than those in maternal or fetal plasma. ir-ET concentrations in neonatal urine on day 1 after birth were below the detection limit (< 0·1 pmol/l) by radioimmunoassay in 70% of the cases examined but on day 5 after birth ir-ET was present at measurable concentrations in all cases.
It is suggested that endothelin may act as a circulating hormone during pregnancy and labour in both maternal and fetal circulations.
Journal of Endocrinology (1991) 129, 301–307
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ABSTRACT
Ovaries from pregnant and postpartum Sprague–Dawley rats were examined for content of immunoreactive β-endorphin by radioimmunoassay, and for its localization by the peroxidase-antiperoxidase technique. In addition, the molecular forms of β-endorphin immunoreactivity were separated by gel chromatography and reverse-phase high performance liquid chromatography (RP-HPLC). Ovaries from rats early in pregnancy showed intense granular cytoplasmic staining of luteal cells, with an even distribution of granular material throughout the cytoplasm. By middle to late pregnancy the staining pattern was changed, with immunoreactive material showing a less granular and unevenly distributed staining pattern and with some areas of the cytoplasm totally devoid of immunoreactive material. The concentrations of immunoreactive β-endorphin measured during pregnancy were significantly lower than levels in mature non-pregnant rat ovary. The ovarian concentration of immunoreactive β-endorphin fell progressively during pregnancy and early lactation, returning to normal cyclic rat levels at 20 days post partum. The ovarian concentration of β-endorphin-like material was lowest at 6 days post partum (0·53 ± 0·08 ng/g wet weight; mean ± s.e.m.), representing approximately 10% of the concentration found in pooled ovaries from randomly cyclic adult rats. Gel chromatography revealed only a single peak of immunoreactive β-endorphin, co-eluting with 3·5 kD molecular weight ovine β-endorphin(1–31). This contrasts with gel profiles of adult cyclic rat ovary, where large molecular weight species pro-opiomelanocortin (31 kD) and β-lipotrophin (11·5 kD) are also present. On RP-HPLC the predominant species of low molecular weight immunoreactive material co-eluted with β-endorphin(1–31).
These data show that pregnancy in the rat is associated with marked changes in the levels, cellular localization and chromatographic profiles of ovarian β-endorphin. The aetiology and physiological significance of these changes remains to be established.
J. Endocr. (1986) 108, 343–350
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SUMMARY
The association between duration of gestation and (a) parental height, and (b) mother's parity is examined in 1028 single and 375 twin maternities. With increasing height of mother, duration of gestation increases in multiple pregnancy; the two variables are unrelated in single pregnancy. With increasing parity, duration of gestation increases in multiple pregnancy and decreases slightly in single pregnancy. It is suggested that these observations provide support for the view that the early onset of labour in multiple pregnancy may be due to the size of the foetuses.
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restriction (MNR) in which nutrient-restricted mothers eat 70% of the global diet of ad libitum -fed controls throughout pregnancy ( Nijland et al . 2007 ). This degree of maternal, and subsequent fetal, nutrient restriction produces decreased nutrient
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Plasma concentrations of inhibin A and inhibin B during pregnancy and early lactation in chimpanzees were determined by enzyme-linked immunosorbent assay (ELISA). Plasma samples were taken from five pregnant chimpanzees at 6-9, 10, 20 and 25 weeks of pregnancy, and following parturition. Throughout pregnancy and the early postpartum period, circulating inhibin A and inhibin B concentrations remained low, at similar levels to those during the normal menstrual cycle in chimpanzees. Concentrations of inhibin A in the placental homogenate were high enough to be measured by the ELISA and by bioassay, whereas circulating inhibin bioactivities in late pregnancy were too low to be measured. Plasma concentrations of FSH remained low with no significant changes throughout pregnancy and the postpartum period. Plasma concentrations of oestradiol-17beta and progesterone at 25 weeks of pregnancy were much higher than normal menstrual cycle levels. It was concluded that in chimpanzees the levels of circulating inhibin A and inhibin B remained low throughout pregnancy and the early postpartum period, and that the concentrations of bioactive dimeric inhibin did not increase towards the end of pregnancy. The suppression of circulating FSH levels during pregnancy is suggested to be controlled by steroid hormones that increased significantly in late pregnancy, and the present findings further suggest that the secretory pattern and role of inhibin during pregnancy in chimpanzees may be different from that in human and other primates.
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Department of Physiology, Faculty of Medicine, University of Manitoba, 770 Bannatyne Avenue, Winnipeg, Canada, R3E 0W3
(Received 7 April 1977)
Binding of prolactin to the rat mammary gland is low during pregnancy and only increases at parturition (Holcomb, Costlow, Bushchow & McGuire, 1976). Holcomb et al. (1976) have suggested that failure to demonstrate binding of prolactin may be related to occupancy of the prolactin receptor by placental lactogen. However, the rabbit apparently does not produce a placental lactogen (Kelly, Tsushima, Shiu & Friesen, 1976; McNeilly & Friesen, 1977), and it was therefore of considerable interest to determine whether the results of binding of prolactin to the rabbit mammary gland during pregnancy showed significant differences from those obtained in the rat.
Mammary glands were taken from pregnant New Zealand White rabbits killed by an i.v. overdose of sodium pentobarbitone on each of days 10, 15, 20, 25, 28, 29, 30 and
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Miller, Owen & Emmens (1968) described the changes in uridine incorporation into uterine and vaginal RNA during early pregnancy and pseudopregnancy in the mouse and discussed their significance. A large increase in uridine incorporation occurred in the uteri in both conditions between 10.30 hr. on day 2 and 10.30 hr. on day 3, with a further increase from day 4 onwards only in the uteri of pregnant mice. The former increase is in both cases believed to reflect increasing ovarian oestrogen secretion, a conclusion supported by the studies of Finn & Martin (1967), Martin & Finn (1968) and Galassi (1968). In view of the widely held belief in a discrete surge of ovarian oestrogen on day 4 of pregnancy in the rat (Tic, Marcus & Shelesnyak, 1967) it was considered desirable to study the corresponding changes in this species.
Randomly bred female rats of the Wistar strain, weighing 200–280 g.,
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In a recent study of renal function in supposedly pregnant rabbits, much time and effort was wasted because about half the mated females failed to become pregnant. On retrospective analysis, the daily sodium excretion was different in the animals which became pregnant as compared with those which failed to become pregnant and which were presumably pseudopregnant. The main difference was apparent on day 4 after mating. We are now using sodium excretion as a simple diagnostic test of pregnancy in rabbits.
Fifteen animals were kept in metabolism cages for 20 days before mating and for the duration of the supposed pregnancy. Only eight of the 15 actually became pregnant. All the urine excreted by each animal each day was collected, its volume measured and its sodium concentration estimated by flame photometry. For each animal the mean daily excretion during the 20-day control period was defined as 100%. Figure 1 shows
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SUMMARY
Adrenal and plasma corticosterone levels were determined in rat foetuses and in intact or adrenalectomized mothers during late pregnancy. Foetal adrenal and plasma corticosterone concentrations reached a peak on day 19 of pregnancy, while maternal plasma corticosterone increased on day 18 and remained high until parturition. From day 18, mothers adrenalectomized on day 14 had corticosterone levels similar to those of intact pregnant rats. At every stage of gestation (except day 21) plasma corticosterone levels were higher in the foetuses than in the mothers. The corticosterone concentration in the maternal plasma correlated with the number of live foetuses during the last 3 days of gestation.
These results suggest that corticosterone can cross the placenta from foetus to mother as early as day 18 and that the foetus contributes to the maternal corticosterone pool after day 18.
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Institute of Obstetrics and Gynaecology, Queen Charlotte's Hospital, Goldhawk Road, London, W6 OXG
(Received 4 September 1974)
It is well established that the rise in total plasma cortisol which follows the administration of corticotrophin (ACTH) or tetracosactrin is greater in late pregnancy than in non-pregnant women (Jailer, Christy, Longson, Wallace & Gordon, 1959; Campbell, Bain, Dewhurst & Fotherby, 1970; Johnstone & Campbell, 1974). However, it is not clear whether this can be completely explained by the increased corticosteroidbinding globulin levels in pregnancy (Doe, Fernandez & Seal, 1964; De Moor, Steeno, Brosens & Hendrikx, 1966) or whether there is a true rise in tissue exposure to unbound cortisol. In non-pregnant subjects, 1·0 mg depot tetracosactrin (Ciba) appears to give a maximal adrenal stimulus, at least over the first 4 h (Besser, Butler & Plumpton, 1967; Nelson, Neill, Montgomery, Mackay, Sheridan & Weaver, 1968), and we have described the total 11-hydroxycorticosteroid patterns
