Effect of prostaglandins on in vitro synthesis of progesterone and oestradiol-17β in placenta from early human pregnancy

In vitro synthesis of progesterone and estradiol-17β from endogenous precursors was studied in the placenta from women in early stage of gestation (< 7 weeks). Radioimmunoassay techniques were used to measure progesterone and estradiol-17β.It was shown that placental tissue from as early as six weeks of gestation can synthesize both progesterone and estradiol-17β in vitro. Prostaglandins F_2α and E₂ in concentration of 100 μg/ml of the incubation media did not have any significant effect on the in vitro synthesis of progesterone and estradiol-17β in the placental tissue.It seems unlikely that the abortifacient effect of natural prostaglandins PGE₂ and PGF_2α is due to their direct action on the synthesis of progesterone and estradiol-17β in the placenta.     

Fetal and maternal endocrine changes associated with parturition in the goat

In 4 goats maternal jugular plasma concentrations of progesterone started to decline before labor commenced, but levels remained elevated above basal concentrations throughout parturition. Fetal and maternal plasma concentrations of estrogen rose before and during labor, increasing markedly just prior to fetal delivery. Fetal carotid plasma glucocorticoid concentrations appeared to rise over the 5 days prior to parturition, but a significant increase was only noted during labor. Maternal plasma concentrations of glucocorticoids were significantly lower than fetal plasma concentrations of glucocorticoids. Estradiol-17α was the predominant estrogen in both fetal and maternal plasma, less estrone was detected and apparently little estradiol-17β was present.No good correlation was found between plasma progesterone or estrogen and parturient uterine activity; the latter lasted from 22 to 78 hours, with the most dramatic increase occurring close to delivery. It is probable that other agents are involved in controlling uterine activity during parturition in the goat.     

Inhibition of progesterone secretion by a 3 beta-hydroxysteroid dehydrogenase inhibitor in late pregnant sheep

The role of progesterone in the initiation of parturition in the sheep is unclear. Whether a decrease in plasma progesterone is the essential prerequisite for the initiation of parturition or whether other factors also maintain uterine quiescence until delivery is not known. The effect of withdrawal of progesterone on the initiation of parturition has been investigated by intravenous administration of trilostane, a 3 beta-hydroxysteroid dehydrogenase delta 5-4 isomerase inhibitor, to late pregnant sheep. Twenty-five or 100 mg trilostane caused a precipitous decrease in plasma progesterone to about 30% of preinjection levels. Progesterone remained depressed for up to 7 days after treatment. 13,14-Dihydro-15-keto-prostaglandin F2 alpha (PGFM) became elevated between 7 and 36 h after trilostane injection but gradually returned to preinjection levels during the subsequent 36 h, at a time when plasma progesterone was still depressed. Four of 11 animals treated with 100 or 200 mg trilostane aborted prematurely at a time when plasma PGFM was maximal and plasma progesterone minimal. There were no consistent changes in plasma estradiol-17 beta or ovine placental lactogen concentrations after treatment with trilostane. It is suggested that a decrease in plasma progesterone will cause a transient increase in plasma PGFM concentrations which can lead to the premature initiation of parturition. In some instances the myometrium does not appear to respond to the elevated PGFM concentrations even when the estrogen:progesterone ratio is elevated by a decrease in plasma progesterone.     

Oxytocin-stimulated production of prostaglandin F2α by isolated endometrium of rabbit: Modulation by ovarian steroids

To test the hypothesis that ovarian steroid hormones modulate oxytocin-induced release of prostaglandin F_2α (PGF_2α) from uterine endometrium, 2 ovariectomized rabbits were pretreated with progesterone (5 mg/day for 10 days), 2 with estradiol-17β (25 μg/day for 10 days), 2 with both steroids, and one with sesame oil only. On the last day of treatment, endometrial fragments were excised and incubated in vitro with or without oxytocin (100 μU/ml). Although endometrium from rabbits pretreated with combined steroids released more PGF_2α immediately after excision than did tissue from animals pretreated with either steroid by itself, endometrium from animals pretreated with estrabdiol-17β alone released the most PGF_2α during sustained incubation in vitro. Moreover, only this tissue exhibited significant oxytocin-dependent release of PGF_2α. At the dosages used, progesterone completely antagonized both of these effects of estradiol-17β. The results support the hypothesis that ovarian steroid hormones regulate oxytocindependent release of PGF_2α from endometrial cells. A possible mechanism of action is suggested.     

Oxytocin and bovine parturition: a steep rise in endometrial oxytocin receptors precedes onset of labor.

Oxytocin receptors were measured in myometrium and intercaruncular endometrium of cows during pregnancy and parturition. Concentrations of estradiol-17 beta, estrone, and progesterone in peripheral blood were also measured. Receptor concentrations in the endometrium rose almost 200-fold from Day 20 to term (p < 0.0001, ANOVA), from 40 +/- 11 to 7300 +/- 1430 fmol/mg protein. Myometrial receptor concentrations increased 10-fold from 180 +/- 36 fmol/mg on Day 20 to 1850 +/- 360 fmol/mg protein at term (p < 0.0001, ANOVA). During labor, endometrial receptors (6600 +/- 1300 fmol/mg) remained at prelabor values, whereas myometrial receptor concentrations had decreased to 1190 +/- 316 fmol/mg (not significant) and declined further postpartum. Plasma concentrations of progesterone declined from 4-5 ng/ml to about 2 ng/ml between Days 250 and 282 and dropped to < 0.2 ng/ml shortly before delivery. Plasma concentrations of estrone and estradiol-17 beta were below 10-20 pg/ml until Day 230. Estrone concentrations were significantly (p < 0.05) increased by Day 250 and estradiol-17 beta by Day 270, and then both rose rapidly. During labor, plasma estrone was 1135 +/- 245 pg/ml and plasma estradiol-17 beta was 226 +/- 131 pg/ml. The molar ratio of estrone and estradiol-17 beta to progesterone rose from less than 0.01 to 4.4 during labor, and was correlated with oxytocin receptor concentrations in endometrium (r = 0.5160, p < 0.001), but not those in myometrium (r = 0.0122). The regulation of oxytocin receptors by ovarian hormones in the two tissues may therefore differ.(ABSTRACT TRUNCATED AT 250 WORDS)     

A developmental study on the capacity of rabbit granulosa cells to respond to trophic hormones and secrete progesterone in vitro

To determine when undifferentiated rabbit granulosa cells first develop the capacity to secrete progesterone, pieces of intact ovaries from neonatal rabbits (newborn—30 days old) and pure granulosa cells from 150–1200 μm follicles at 60–600 days old were cultured in vitro for 6–10 days with human chorionic gonadotropin (HCG), Pergonal (LH/FSH), dibutyryl cyslic AMP (Bu₂CAMP), prostaglandin E₂, estradiol-17β, and as controls. The culture medium was collected every 2 days, and progesterone, estrone, and estradiol-17β were measured by radioimmunoassay.None of the neonatal ovaries or granulosa cell cultures secreted estrone or estradiol-17β spontaneously or in response to stimulation by gonadotropins, Bu₂CAMP, or prostaglandin E₂.Control cultures of newborn and 7-day-old ovaries did not secrete progesterone, but ovaries from 17- and 30-day-old rabbits did. Gonadotropins and Bu₂CAMP induced progesterone secretion in 7-day-old ovaries and stimulated its production 5-10-fold in ovaries at 17 and 30 days old, but prostaglandin E₂ and estradiol-17β were without effect.Granulosa cells from all antral follicles (200–1200 μm) secreted progesterone spontaneously, and its production was stimulated 100–1000-fold with gonadotropins and Bu₂CAMP, but not with estradiol-17β or prostaglandin E₂. In contrast, granulosa cells from 100–150 μm preantral follicles from 200-day-old animals did not secrete progesterone under these culture conditions.These results demonstrate that rabbit granulosa cells differentiate the capacity to secrete progesterone at the time the primary follicle develops an antrum, and suggest the differentiation process involves the acquisition of the capacity to respond to gonadotropins perhaps by the synthesis or unmasking of gonadotropin receptors.     

Cell growth and cell proliferation may be dissociated in the mouse uterine luminal epithelium treated with female sex steroids

The mouse uterine epithelium under various hormonal regimes is a good system to identify biochemical events associated with cell growth, DNA synthesis and cell division. This is because estradiol-17β stimulates the cells to undergo a synchronized wave of DNA synthesis and cell division. Estriol, on the other hand, also stimulates DNA synthesis but because of the rapid loss of this hormone from the tissue some of the cells abort, giving a constant epithelial cell number. Three days of progesterone pretreatment, however, completely suppresses the estradiol-17β-induced wave of DNA synthesis and cell proliferation.Using these hormonal treatments we have shown that both estradiol-17β and estriol stimulate protein and rRNA synthesis with the concomitant increase of protein and rRNA per mg of DNA. These macromolecules accumulated in direct proportion to the fraction of cell committed to DNA synthesis. Estriol, however, did not sustain the growth responses and at the peak of DNA synthesis both rRNA and protein synthesis had returned to control levels. Progesterone pretreatment, despite inhibiting the proliferative response, failed to inhibit any of the estradiol-17β-induced increases in protein and rRNA synthesis. Indeed 12 h after estradiol-17β injection the cells had identical protein and rRNA contents, regardless of whether they had been exposed to progesterone or not.The present data therefore suggests that in the uterine epithelium cell growth as defined by protein and rRNA accumulation and DNA synthesis represents two independently regulated pathways.     

Serum LH,progesterone and estradiol-17β levels throughout the ovarian cycle,during the early stage of pregnancy and after the parturition and the abortion in the common marmoset,Callithrix jacchus

In the ovarian cycle of common marmosets, serum progesterone began to increase at two to three days after estradiol-17β or LH surge, attained a peak of 25–70 ng/ml and then declined to a level of under 2 ng/ml before the ensuing rise in estradiol-17β and LH. Serum estradiol-17β increased to 700–5,500 pg/ml during the luteal phase, synchronizing with progesterone. It is suggested that the corpus luteum secreted estradiol-17β as well as progesterone. The cycle length as determined from the interval between successive LH surges was approximately 28 days. During the luteal phase, the levels of progesterone and estradiol-17β were higher than in Old World monkeys and women, but marmosets were not accompanied by any clinical symptoms due to excessive progesterone and estradiol-17β. This suggests that such unresponsiveness to progesterone and estradiol-17β in marmosets reflects the small amount of estradiol-17β receptor and presumably also the lower function of the post receptor system. Recovery of the post-partum ovarian cycle in two marmosets differed from that observed in Old World monkeys and women. The first LH surge was found on the ninth and tenth day after parturition and the first ovulation led to the next pregnancy. This suggests that the suckling stimulus of newborns in the common marmoset does not cause any delay in recovery of the ovarian cycle. In three cases of abortion, the recovery of the ovarian cycle was almost the same as that in the case of normal parturition: the first LH surge appeared on the 10th, 14th, and 34th day after abortion.     

Treatment with a single vaginal suppository containing 15-methyl PGF2α methyl ester at expected time of menstruation

Termination of early pregnancy, by vaginal administration of prostaglandin analogues, one to three weeks after the first missed menstrual period, has advantages and disadvantages in comparison with vacuum aspiration. Some of these may be reduced if the patient is treated earlier. In the present study the effect and safety of one vaginal administration of 2.5 to 3 mg 15-methyl-PGF_2α methyl ester around the expected time of menstruation was evaluated in 16 women exposed to the risk of pregnancy.The overall number of treatment cycles was 35 and pregnancy was confirmed by plasma β-HCG in eight. The treatment resulted in bleeding in all the pregnant cycles while in the nonpregnant ones it only provoked spotting and bleeding did not begin until the expected time of menstruation. Treatment with 2.5 mg 15-methyl-PGF_2α methyl ester resulted in complete abortion in one of three women. If the dose was increased to 3 mg all five treated women aborted. In nonpregnant patients no changes in the levels of estradiol-17β or progesterone at any time during the 24-hour observation period were found. Serum cortisol and prolactin but not TSH levels started to increase two hours after the start of treatment and reached a maximum after five hours. The increase coincided with the onset of uterine pain.Ovulatory cycles as judged from basal body temperature occurred in the first menstrual cycle following treatment in all nonpregnant patients. Although possible to use as a “once a month treatment” it seems preferable since the dose is the same, to postpone treatment until menstruation is delayed for a week or more.     

Peripheral plasma levels of progesterone in pregnant goats and in pregnant goats treated with prostaglandin F2a

Prostaglandin or prostaglandin analogues have been shown to be luteolytic in the pregnant goat. In this study the temporal changes in the plasma concentrations of progesterone during pregnancy and after administration of PGF2a to pregnant goats are described. PGF2a administration to pregnant goats at 30 and 65 days after breeding induced abortion within 34 to 75 hours. These abortions were accompanied by estrus and profuse muco-hemorrhagic discharges. When PGF2a was administered to pregnant goats 140 or 142 days after breeding, premature parturition occurred within 42 to 76 hours. Live kids were delivered in all cases. The plasma levels of progesterone in all pregnant goats showed dramatic decreases within 24 hours after the prostaglandin injections and continued to decrease gradually until abortions or premature parturition. Thereafter, the progesterone levels remained low for several days.     

The effect of estradiol-17β and actinomycin D on the release of PGF and PGE from separated cells of human endometrium

Estradiol-17β selestively stimulated the release of PGF from separated glandular but not stromal cells of human secretory endometrium (p<0.025) but had no effect on PGF release from either type of cells obtained from proliferative endometrium. PGE release was not affected by estradiol-17β. Actinomycin D did not antagonise the effect of estradiol-17β on PGF release from secretory, glandular cells. Basal release of PGF from these cells was stimulated by actinomycin D alone (100 ng/ml) (p<0.025) and PGE release stimulated in the presence of estradiol-17β. Actinomycin D had no effect on PGF or PGE release from proliferative endometrium. These findings suggest that estradiol-17β stimulates PGF release by a mechanism that does not affect PGE release and which is not dependent on the synthesis of new protein. The basal release of PGF and PGE by glandular cells of secretory endometrium in vitro is regulated by protein/proteins which reduce PG release.     

Intravaginal PGE2 in early abortion

Intravaginal PGE2 was administered to 10 women in early (less than 50 days) pregnancy. Complete abortion was effected in 8, an incomplete abortion in one and one was a failure. Significant systemic side effects were noted in all subjects. Urinary hCG excretion rates prior to and on the 2nd and 14th day after PGE2 showed a decrease in all successfully aborted subjects and an initial decrease but a subsequent rise in the failure subject. Plasma concentrations of progesterone and estradiol-17β showed no significant alterations during the early (less than 2 hours) administration of PGE2 but decreased significantly in all subjects just prior to expulsion, and at intervals thereafter. Estradiol-17β and progesterone alterations appeared to parallel each other indicating a common source, the corpus luteum. The mechanism by which PGE2 may effect early abortion is discussed.     

Release of prostaglandin F2α during the bovine peripartal period

Progesterone, estrone and 15-keto-13,14-dihydro-PGF_2α levels were determined in the peripheral blood circulation during the peripartal period in 12 cows. Plasma concentrations of progesterone showed a gradual and continuous decrease during the last 60 days before parturition. This gradual decrease was followed by an abrupt decline in the progesterone concentration occurring 24–48 hours before delivery. The plasma levels of estrone started to increase about 30 days prior to parturition with high concentrations attained during the last days of pregnancy. After delivery the estrone content decreased to baseline levels. Increased levels of the PGF_2α metabolite were recorded 24–48 hours before parturition. These increased PGF_2α metabolite levels occurred before or in conjunction with prepartum luteolysis. Prostaglandin metabolite levels remained high during parturition and returned to baseline 10–20 days after delivery.     

Effect of fenprostalene, a PGF(2)alpha analogue, on plasma levels of estradiol-17beta and progesterone in cyclic heifers

Following a 40-day acclimatization period, 12 cyclic beef heifers entered a 95- to 101-day test period. Prior to fenprostalene treatment, all animals were studied through two normal estrous cycles. Plasma samples were obtained daily from all animals during the course of the study and were assayed for estradiol-17beta and progesterone. Group 1 heifers (n=6) were then treated with fenprostalene at mid-cycle during two subsequent cycles. This treatment was accomplished by treating the animals 11 days after the first clinically observed signs of estrus following Study Day 21 and treating them again 11 days later. Each treatment consisted of a subcutaneous injection of 1.0 mg fenprostalene. The animals were studied through two or three estrous cycles following the second injection. The Group 2 animals (n=6) were maintained as untreated controls through a corresponding period. Fenprostalene induced estrus in five of six treated heifers within 5 d following the first injection and in five of six heifers within 3 d following the second injection. The mean time to estrus was 3.4 d (+/- 1.1 d SD) following the first injection and 2.2 d (+/-0.8 days SD) following the second injection. No significant differences were found in the plasma levels of estradiol-17beta and progesterone when comparing fenprostalene-induced cycles to those that occurred naturally. The fenprostalene injection reset the estrous cycle without changing the nature of the cycle. The time of clinically detected estrus usually coincided with a sharp peak in estradiol-17beta concentration.     

Inhibition of uterine prostaglandin-F2α production by bovine conceptus secretory proteins

The effect of bovine conceptus secretory proteins (CSP) on uterine prostaglandin (PG)-F_2α production was evaluated in dairy cattle following injection of estradiol-17β. Intrauterine injections of dialyzed serum proteins (Control, n=5) or CSP (n=5) were administered from days 15 through 18 post-estrus. Following intrauterine treatments on day 18, all cows were injected with E₂ (3 mg) to stimulate uterine PGF_2α production. Plasma concentrations of progesterone (P₄) and 15-keto-13,14-dihydro-PGF_2α (PGFM) were determined by RIA. The PGFM responses following E₂ challenge were decreased (p<0.01) for cows receiving CSP versus serum proteins into the uterine lumen. Individual PGFM, P₄ and cycle length responses are discussed. Data suggest that proteins secreted by the bovine conceptus suppress uterine PGF_2α production during pregnancy recognition in the cow.     

Hormonal changes in spontaneous and aglépristone-induced parturition in dogs

To increase our understanding of the endocrine changes associated with parturition in dogs, plasma concentrations of progesterone (P4), 15-ketodihydroprostaglandin F(2alpha) (PGFM), estradiol-17-beta (E2beta), cortisol, ACTH, prolactin (PRL), LH, and FSH were measured in six spontaneously whelping bitches and in six bitches in which parturition was induced with the progesterone-receptor blocker aglépristone on day 58 of pregnancy. Expulsion of pups in the induced group took place in the presence of P4 concentrations that were still elevated. PGFM concentrations increased before parturition in both groups, but levels were lower in the induced bitches. PGFM levels reached a maximum in both groups during parturition and quickly decreased in the spontaneously whelping group after parturition, but remained elevated in the induced group. In both groups, cortisol concentrations reached similar maximum levels during the last 30 h before the onset of expulsion. During the 3 days postpartum, cortisol concentrations were higher in the induced group. The highly variable ACTH concentrations did not differ significantly throughout the study within or between groups. In both groups, E2beta concentrations decreased and PRL concentrations increased between the late gestational period and the 30-h period before parturition. Concentrations of both LH (spontaneously whelping group) and FSH (both groups) decreased between late gestation and the postpartum period. The results of this study illustrate the hormonal changes around parturition in the bitch, and reveal that aglépristone-induced parturition is associated with still incomplete luteolysis, an altered PGFM profile, and elevated postpartum cortisol concentrations as compared with spontaneously whelping dogs.     

Hormone changes occurring during second trimester abortion induced with 15(S)-15-methyl prostaglandin F2α

Changes in progesterone, human placental lactogen (HPL), cortisol and estradiol-17β were measured during second trimester abortion induced by I.M. 15-methyl PGF2α. A rapid decline in progesterone and HPL was found, indicating perhaps an initial effect on the placenta. A rapid rise in cortisol was found, but it is not clear if this is due to stress or part of the termination mechanism. The changes of estradiol were not as distinct and may reflect opposite effects of the prostaglandin on the placenta and adrenals. Similar hormonal changes were observed regardless of the duration of gestation.     

The roles of pregn-5-ene-3β,20α-diol and 20α-hydroxy steroid dehydrogenase in the control of progesterone synthesis preceding parturition and lactogenesis in the rat

1. The activity of 20α-hydroxy steroid dehydrogenase in rat ovarian corpora lutea increased at least 50-fold between 2 days before and 2 days after parturition, and then fell gradually during lactation. The activity of 3β-hydroxy Δ⁵-steroid dehydrogenase decreased by 50% at parturition but remained constant at other times. 2. The 20α-hydroxypregn-4-en-3-one/progesterone concentration ratio in the ovary fell tenfold between 1 day before and 1 day after parturition, in contrast with the increase of the ratio for these steroids in plasma. 3. Pregnenolone was metabolized in intact cells or cell-free systems either to pregn-5-ene-3β,20α-diol and then to 20α-hydroxypregn-4-en-3-one by 20α-hydroxy steroid dehydrogenase and 3β-hydroxy Δ⁵-steroid dehydrogenase respectively, or directly to progesterone by the latter enzyme. The relative activities of these pathways appeared to reflect the relative amounts of the two enzymes and the concentrations of their respective coenzymes NADPH and NAD⁺. 4. From these and other observations it was concluded that the cessation of progesterone secretion, which precedes parturition and lactogenesis at the end of pregnancy, is partly due to the redirected metabolism of pregnenolone away from progesterone and towards 20α-hydroxypregn-4-en-3-one as the secreted end product. This is primarily the consequence of the sharp increase in the activity of 20α-hydroxy steroid dehydrogenase. This mechanism is super-imposed on the already declining rate of net Δ⁴-steroid release by the ovary. 5. A relationship of these pathways to subcellular compartments of luteal cells is proposed.     

Control system for detection of the illegal use of naturally occurring steroids in calves

Within the scope of the National Plan for Hormone Control in The Netherlands, a study was performed to develop a system for control of the illegal use of three naturally occurring hormones [oestradiol-17β (E₂-17β), testosterone (T), progesterone (P)] for fattening purposes in animal production. Using a specific high-performance liquid chromatographic—radioimmunoassay method, reference values were established for concentrations of E₂-17β, T and P and some of their metabolites in blood plasma and urine from untreated male and female veal calves. E₂-17β levels of both male and female calves were <0.01 μg/l in blood plasma and <0.2 μg/l in urine. For male veal calves levels of T and epitestosterone (epiT) in blood plasma and urine varied widely. The P levels were <0.1–0.3 μg/l in blood plasma and <0.6–10 μg/l in urine from both male and female calves. To investigate the effect of anabolic treatment on the hormone levels in plasma and excreta, male veal calves were injected, subcutaneously into the dewlap, with a solution containing 20 mg of E₂-17β benzoate and 200 mg of T propionate in 5 ml of arachis oil. Only the levels of E₂-17β and E₂-17α in blood plasma and excreta were elevated until about one week after injection, compared with the untreated control calves and the reference values. T and epiT levels were similar in plasma and excreta from both untreated and treated animals.     

Peripheral plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2α and progesterone around luteolysis and during early pregnancy in the goat

Peripheral plasma concentrations of 13,14-dihdyro-15-keto-prostaglandin F_2α (PGFM) and progesterone were determined during both luteolysis in the oestrous cycle and early pregnancy in four goats. Luteal regression, characterised by decreasing progesterone concentrations, began on day 12 or 13. PGFM concentrations showed a pulsatile pattern around this time, with peak concentrations increasingly markedly as progesterone levels fell and oestrus approached. During early pregnancy progesterone concentrations did not fall after day 12 and no marked elevation of PGFM above basal values of 50–150 pg/ml was detected.