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PubMed1981

Facilitation and inhibition of the estrogen-induced luteinizing hormone surge in the rat by progesterone: effects on cytoplasmic and nuclear estrogen receptors in the hypothalamus-preoptic area, pituitary, and uterus.

The possibility that inhibition and facilitation of estrogen-induced LH surges by progesterone could be associated with effects of this steroid on the concentration, subcellular distribution, or molecular properties of estrogen receptors in the hypothalamus-preoptic area (HPOA) and pituitary was investigated. Immature rats (28 days old) that received Silastic capsules containing estradiol-17 beta in oil (150 micrograms/ml) at 0900 h had LH surges between 1700 and 2000 h on day 29. This treatment led to depletion of cytoplasmic estrogen receptors (to 25-35% of control levels) and their accumulation in the nucleus. Insertion of crystalline progesterone implants concomitantly with estradiol implants or 24 h later resulted in blockade or enhancement of the LH surge, respectively. Progesterone administered in either mode did not significantly after the levels of estrogen receptors in the HPOA and pituitary; however, progesterone did suppress the quantity of both cytoplasmic and nuclear estrogen receptors in the uterus when administered in conjunction with estradiol for 24 h oe for 8 h after 24-h estrogen priming. The binding affinity and sedimentation properties in sucrose gradients of cytoplasmic estrogen receptors were unchanged by progesterone treatment. The specificity of the effects of progesterone on LH secretion was examined. Testosterone, dexamethasone, and the synthetic progestin R5020 (17,21-dimethyl-19-nor-4,9-pregnadien-3,20-dione) also inhibited LH surges when injected 8 h after placement of estradiol implants in 28-day-old rats. Only progesterone and R5020 brought about premature and sustained LH release when given to estradiol-primed rats at 0900 h on day 29. None of these compounds interfered directly with the binding of [3H]estradiol to cytoplasmic or nuclear receptors. In conclusion, modulation by progesterone of the estrogen-induced LH surge does not seem to result from effects on neural and hypophysial estrogen receptors. In contrast, suppression of uterine estrogen receptors by progesterone may account in part for antagonism by this steroid of estrogen-stimulated uterine growth.

Animals↗

PubMed1981

The endocrine basis of the synergistic suppression of luteinizing hormone by estradiol and progesterone.

The basis of the synergism between estradiol and progesterone in suppressing tonic (pulsatile) LH secretion was examined in the ewe, making use of the observation that progesterone exerts its inhibition selectively on LH pulse frequency, while estradiol decreases only pulse amplitude. To accomplish this, we analyzed changes in LH pulse patterns produced by a low level of progesterone in ovariectomized ewes treated with Silastic estradiol implants from the time of gonadectomy. A serum progesterone level of about 1 ng/ml was chosen because it inhibits LH only in the presence of estradiol. Under these circumstances, a decrease in LH pulse amplitude during progesterone treatment would suggest that progesterone increased the response to the existing level of estradiol; a decrease in pulse frequency would suggest that estradiol increases the effectiveness of progesterone. It was found that the low level of progesterone produced a decrease in LH pulse frequency in estradiol-treated ovariectomized ewes without altering pulse amplitude. These results are consistent with the hypothesis that the synergism of these two steroids reflects, at least in part, an estradiol-induced increase in the sensitivity of the central nervous system to the negative feedback action of progesterone.

Animals↗

PubMed1982

Stimulation of progesterone and prostaglandin E accumulation by luteinizing hormone-releasing hormone (LHRH) and LHRH analogs in rat granulosa cells.

The present investigation was performed to characterize the accumulation of progesterone and prostaglandin E (PGE) by rat granulosa cells exposed to LHRH and LHRH analogs in vitro. Granulosa cells were obtained from immature rats 48 h after the injection of 20 IU PMS gonadotropin and incubated for up to 5 h, followed by determination of the total progesterone and PGE accumulated in cells and medium. LHRH and several LHRH agonists, at concentrations of 10-2000 ng/ml, caused 2- to 3-fold increases in progesterone accumulation. This stimulation was consistently much less than the 15- to 30-fold increase produced by LH or FSH. A LHRH agonist also stimulated PGE synthesis by rat granulosa cells, but in this case the stimulation was similar in magnitude and time course to the effect of LH. In addition, the injection of a LHRH agonist into hypophysectomized, PMS gonadotropin-treated immature rats resulted in elevated ovarian PGE content 5 h later. The effect of LHRH on progesterone and PGE accumulation by rat granulosa cells was blocked by a LHRH antagonist. Lh stimulation of progesterone and PGE accumulation, on the other hand, was not affected by this antagonist. Incubation of granulosa cells with LHRH agonist did not reduce the progesterone or PGE response to LH or FSH, even at suboptimum concentrations of gonadotropin. The presence of 10(-7) M testosterone did not modify the effect of a LHRH agonist on basal or LH-stimulated progesterone and PGE accumulation. In acute incubations of granulosa cells from mature follicles, therefore, LHRH specifically stimulates progesterone and PGE accumulation when present alone, and does not modify the stimulation of progesterone accumulation by LH or FSH.

Animals↗

PubMed1986

Effects of progesterone on decidual prolactin production by organ cultures of human endometrium.

The effects of progesterone on decidual PRL (dPRL) production by human endometrium were investigated by culturing explants of proliferative (n = 20) and secretory (n = 12) endometrium in Dulbecco's Modified Eagle's Medium supplemented with 10 mM HEPES buffer, 0.1% gelatin (wt/vol), and antibiotics for 6 days and in medium containing 50 ng/ml of progesterone for 6-28 days. The culture medium was replaced daily, and the spent medium was assayed for dPRL. Representative explants were fixed for histological examination after 1, 2, 7, 14, and 28 days in vitro. When explants of endometrium obtained throughout the cycle were cultured in the presence of progesterone, dPRL production was stimulated. Proliferative endometria required 2-5 days in culture before dPRL was measured in the medium. Thereafter, dPRL production increased gradually for the duration of the experiment. Progesterone also induced glandular secretion and stromal differentiation (decidualization) in these tissues. Cultures of proliferative endometrium that did not receive progesterone did not produce detectable amounts of dPRL. When explants of secretory endometrium were cultured in DMEM without exogenous progesterone, dPRL was released into the medium for 2-5 days; however, dPRL production by the cultures that did not receive progesterone declined to undetectable levels, while that by the progesterone-treated cultures increased steadily. Explants of both proliferative and secretory endometrium that were fixed for histological examination after 28 days of culture in the presence of progesterone were composed predominately of large stromal cells that resembled the decidual cells of pregnancy endometrium.

Decidua↗

PubMed1986

Inhibitory action of epidermal growth factor on progesterone biosynthesis in hen granulosa cells during short term culture: two sites of action.

The acute effect of epidermal growth factor (EGF) on progesterone biosynthesis by hen granulosa cells in short term culture was investigated. Pretreatment of cells for 5 h with EGF at concentrations of 1000-4000 ng/ml inhibited LH-stimulated progesterone production by 54%. Shorter EGF pretreatment times of 1 and 3 h caused 25% and 35% inhibition of LH-stimulated progesterone production, respectively. In additional experiments, EGF was found to inhibit progesterone production in response to 8-bromo-cAMP (1 mM) and forskolin (100 microM) by 34% and 35%, respectively. EGF had no effect on the conversion of 25-hydroxy-cholesterol or pregnenolone to progesterone, indicating that one site at which EGF inhibits progesterone biosynthesis is distal to cAMP generation, but before the side-chain cleavage step. EGF also inhibited LH-stimulated cAMP production by 32%, but had no effect on forskolin-stimulated cAMP accumulation. This indicated that there was a second site of EGF action in these cells, probably at the level of LH receptor coupling to the adenylate cyclase. Nerve growth factor (4000 ng/ml) had no effect on progesterone production, but fibroblast growth factor (4000 ng/ml) facilitated LH-stimulated progesterone production. The results demonstrate that the acute inhibitory effect of EGF on LH-stimulated progesterone biosynthesis in hen granulosa cells is due to its action at two sites: one at a site before the production of cAMP and the other at a step beyond cAMP generation.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1986

Preparation of monoclonal antibodies to the avian progesterone receptor.

In an effort to obtain additional probes for analysis of the avian progesterone receptor, this receptor was isolated and used to prepare several monoclonal antibodies. Progesterone receptor purified from oviduct cytosol by chromatography on deoxycorticosterone-Sepharose and heparin-agarose was used as the immunizing antigen. Twenty-nine hybridoma cultures which tested positive in an enzyme-linked immunosorbent assay against the receptor preparation were subcloned resulting in establishment of 12 stable cell lines. Of these, 5 produced antibodies capable of complexing receptor-bound progesterone from cytosol as measured by adsorption of receptor-antibody complexes onto antimouse immunoglobulin G-agarose. Each was used to generate ascites and the purified antibodies were designated alpha PR 6, 11, 13, 16, and 22. In addition to precipitating receptor-bound progesterone from cytosol, the antibodies were also effective in increasing the sedimentation velocity of progesterone receptor centrifuged on glycerol gradients, and in recognizing receptor proteins that were resolved by denaturing gel electrophoresis and transferred to nitrocellulose (Western blots). Immunoisolation of receptor was also demonstrated using receptor labeled covalently with the synthetic progestin, R5020. The antibodies were specific for progesterone receptor and did not cross-react with estrogen receptor from the oviduct or glucocorticoid receptor from chick liver. Two antibodies, alpha PR 6 and alpha PR 22, also recognized some mammalian forms of the progesterone receptor. Both antibodies reacted with progesterone receptor from the rabbit uterus and alpha PR 6 recognized human progesterone receptor. Four of the antibodies recognized both A and B forms of the avian receptor while alpha PR6 was specific for the B form.

Animals↗

PubMed1989

Prostaglandins and progesterone secretion in the in vitro perfused pseudopregnant rabbit ovary.

The relationship between progesterone and prostaglandin (PG) secretion in the pseudopregnant rabbit corpus luteum was investigated using isolated in vitro perfused ovaries. Progesterone and PG secretion were measured on days 1, 11, and 18 of hCG-induced pseudopregnancy. The mean progesterone secretion increased significantly from days 1 to 11, and then decreased significantly by day 18. PG secretion was inversely correlated with progesterone secretion, suggesting that PG might inhibit progesterone secretion. To test this hypothesis, indomethacin, an inhibitor of PG secretion, was administered to intact rabbits from days 11-18 of pseudopregnancy and/or on day 18 ovaries were perfused in vitro with indomethacin. Indomethacin administered in vivo, in vitro, or both in vivo and in vitro significantly reduced PG secretion compared to that in controls, but did not affect progesterone secretion. In addition, perfusion of ovaries in vitro with PGF2 alpha did not alter progesterone secretion on either day 11 or day 18. Thus, although there is an inverse relationship between progesterone and PG secretion during pseudopregnancy, PGF2 alpha alone had no effect on progesterone secretion. These results question the hypothesis that PGF2 alpha alone is the luteolytic factor.

6-Ketoprostaglandin F1 alpha↗

PubMed1990

Rapid augmentation by progesterone of agonist-stimulated luteinizing hormone secretion by cultured pituitary cells.

Progesterone acts bimodally at the hypothalamus and at the pituitary gland, the sequelae in vivo being either stimulation or inhibition of gonadotropin secretion depending on a host of preconditions. Pituitary cells in culture were studied to characterize the acute action of progesterone on LH secretion. Preliminary studies established that anterior pituitary cells from adult female rats cultured for three days in 10% charcoal treated fetal bovine serum (c/t FBS) resulted in LH secretory responses to GnRH pulses which were half that for cells cultured in untreated FBS or c/t FBS + 0.2 nM 17 beta-estradiol (E2). Under standardized culture conditions (c/t FBS + E2), GnRH self-potentiation was evident. With this system, 90 min exposure to 200 nM progesterone resulted in a 3-fold augmentation of GnRH-stimulated LH secretion without affecting baseline LH. This action was manifested by 45 but not 15 min of progesterone exposure and was inhibited by simultaneous addition of cycloheximide. The augmentation of agonist-stimulated LH release could be elicited up to 4-5 h after progesterone addition. The estimated half-maximal effect was 10(-9) M, and this concentration of progesterone required E2-pretreatment of the cultured cells. In summary, addition of progesterone to cultured anterior pituitary cells pretreated with E2 leads to a concentration-, time-, and protein synthesis-dependent augmentation of pulsatile GnRH-stimulated LH secretion within 45 min of progesterone exposure. This rapid and unambiguous progesterone action in pituitary cells could function in vivo to define the final magnitude of the preovulatory LH surge.

Animals↗

PubMed1976

Uterine norepinephrine levels as related to plasma and tissue progesterone in pseudopregnant rabbits.

Pseudopregnancy was induced in rabbits by a single iv injection of 100 IU of human chorionic gonadotrophin (hCG). Uterine norepinephrine, located exclusively in adrenergic nerves, was markedly reduced (fluorometric determinations) during the first 6 days of pseudopregnancy and then returned towards pre-injection values. Plasma progesterone (measured by radioimmunoassay) was found to be elevated at days 3,6, and 12 of pseudopregnancy as compared to the very low values of the untreated controls. Although tissue progesterone also increased during pseudopregnancy (fourfold at day 6), there was a somewhat paradoxical relationship between plasma and tissue progesterone. In spite of unchanged plasma levels, tissue progesterone decreased considerably between days 6 and 12. The uterine/plasma progesterone ratio was very high (approximately 28) in non-pregnant (control) animals and ranged between 1 and 3 during pseudopregnancy. These results suggest that there is a causal relationship between the high levels of progesterone in the uterus and the reduced amount of norepinephrine transmitter in the adrenergic nerves in this organ, and that plasma progesterone concentration and the changing progesterone receptor levels regulate uterine progesterone concentration.

Animals↗

PubMed1992

Induction of avidin messenger ribonucleic acid in the chick oviduct by progesterone and other steroids.

Avidin gene expression was analyzed using an avidin immunoassay and RNA hybridization analysis. To ascertain whether the induction of the avidin gene by progesterone remains specific also during secondary restimulation with diethylstilbestrol, chicks were given different steroid hormones or hormone combinations. Progesterone-specific induction of avidin protein and messenger RNA (mRNA) was 15- to 30-fold over the control even after secondary restimulation with diethylstilbestrol. A functional difference between the progesterone response element and glucocorticoid response element was suggested, since dexamethasone alone did not induce avidin in vivo. In spite of progesterone specificity, a combination of progesterone with other steroids nevertheless generated a synergistic increase in the amount of avidin mRNA. This may indicate that binding of progesterone receptor to the progesterone response element may be important to alter the functional activity of other hormone response elements present on the avidin gene. The time response curve of the avidin mRNA induction by progesterone was also determined. Avidin mRNA was detectable 8 h after progesterone induction, and its amount was maximal after 16-24 h. This would indicate that the avidin gene belongs in the so-called late responder genes, which also include chicken ovalbumin, ovomucoid, and lysozyme genes.

Animals↗

PubMed1994

Changes in pulsatile release of neuropeptide-Y and luteinizing hormone (LH)-releasing hormone during the progesterone-induced LH surge in rhesus monkeys.

In previous studies we have shown that the pulsatility of LH-releasing hormone (LHRH) release in gonadectomized monkeys is modulated by input from neuropeptide-Y (NPY) neurons: 1) the endogenous release of NPY in the stalk-median eminence (S-ME) was pulsatile; 2) NPY pulses were temporally correlated with LHRH pulses, with NPY pulses preceding LHRH pulses by approximately 5 min; and 3) infusion of NPY into the S-ME stimulated LHRH release, whereas 4) infusion of antiserum to NPY suppressed endogenous LHRH pulses. It is not known, however, whether ovarian steroid hormones alter the pulsatility of NPY and LHRH release or whether the temporal correlation of NPY and LHRH pulses is maintained during the LH surge. In the present study we examined the changes in pulsatile release of NPY and LHRH in ovariectomized monkeys treated with estradiol benzoate (EB) followed by progesterone or oil. Using push-pull perfusion, perfusate samples from S-ME were collected at 10-min intervals for 15 h. NPY and LHRH concentrations in the perfusates were measured by RIA. Circulating LH levels were also monitored by periodic blood sampling and RIA. Injection of progesterone (sc) after EB induced an LH surge with a peak latency of 7.3 +/- 1.3 h (mean +/- SE) in seven of seven monkeys, whereas oil injection after EB elicited an LH surge in none of seven monkeys. The progesterone-induced LH surge was associated with an increase in LHRH release; the mean, pulse amplitude, and pulse frequency increased significantly (for all, P < 0.05) 4-8 h after progesterone. NPY pulse frequency also increased significantly (P < 0.05) 4-8 h after progesterone treatment, whereas mean release and pulse amplitude did not change in response to progesterone. Oil treatment after EB administration did not alter any parameter of LHRH and NPY pulses. Interestingly, the NPY and LHRH pulses were highly correlated (P < 0.001) in monkeys treated with either EB-progesterone or EB-oil, and NPY pulses preceded LHRH pulses by 4.8 +/- 0.7 and 5.1 +/- 0.6 min, respectively. In summary, 1) an episode of increased LHRH release occurs before and during the progesterone-induced LH surge; 2) acceleration of LHRH pulse frequency and the increase in LHRH pulse amplitude after progesterone are accompanied by acceleration of NPY pulse frequency; and 3) ovarian steroids do not affect the temporal correlation between NPY and LHRH pulses.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1995

Effect of progesterone on hypothalamic oxytocin messenger ribonucleic acid levels in the lactating rat.

We recently reported that sequential administration of estrogen and progesterone and subsequent withdrawal of progesterone increased the level of hypothalamic oxytocin (OT) messenger RNA (mRNA) in the female rat. Both estrogen priming and progesterone withdrawal are critical components of this regimen. Rats experience this ovarian steroid pattern during certain lactational events such as on days 10-12 of lactation or with interruption of nursing for 48-72 h. In the present study, we used Northern blot and in situ hybridization to determine the association between the steroid exposure and the level of OT mRNA during these lactational conditions. Week 1 lactating rats that had pups removed for 24 and 48 h, but not 12 h, had significantly higher serum estradiol concentrations than animals continuously nursing their pups on a comparable day of lactation (F4, 15 = 6; P < 0.005). Serum progesterone levels declined significantly during the 48 h after litter removal (F4, 15 = 130.5; P < 0.0001). Significant increases in OT mRNA levels were found at 48 h, but not 12 or 24 h, after litter removal (F4, 15 = 4.3; P < 0.02). Implantation of progesterone-filled capsules to compensate for the spontaneous decline in progesterone that occurs with interruption of nursing attenuated this increase in OT mRNA levels. OT mRNA was significantly higher in the hypothalamic paraventricular nuclei (P < 0.0002) and supraoptic nuclei (P < 0.002) of nursing interrupted animals receiving empty vs. progesterone-filled implants. Implantation of day 12 lactating rats with progesterone capsules for 5 days before being killed blunted the increase in OT mRNA that normally occurs on this day of lactation. The data highlight the pivotal role of estrogen priming and progesterone withdrawal in the increased expression of the OT gene during select lactational events.

Animals↗

PubMed1995

Regulation of rat mineralocorticoid receptor expression in neurons by progesterone.

We have studied the effects of progesterone on the transcription of the mineralocorticoid receptor (MR) gene in neurons in vitro and in vivo. Progesterone treatment caused a 2.5-fold increase in activity of the MR promoter in transiently transfected N2A neuroblastoma cells. Similarly, MR promoter activity in GH3 pituitary cells was increased 2-fold after treatment with the specific progesterone receptor agonist R5020, with an even greater induction after priming with 17 beta-estradiol. Progesterone treatment also produced a dose-dependent increase in MR messenger RNA (mRNA) levels in primary hippocampal neuron cultures. In vivo, chronic administration of progesterone to estrogen-primed adrenalectomized/ovariectomized rats significantly increased MR mRNA levels in all hippocampal subfields, as determined by semiquantitative in situ hybridization histochemistry. Whereas chronic estradiol treatment decreased MR mRNA levels in the hippocampus, progesterone administration in the absence of estradiol priming was without any effect. These results indicate that 1) progesterone increases MR mRNA levels in vitro and in vivo; 2) the stimulatory effects of progesterone are at least partially mediated by induction of MR promoter activity; and 3) estrogen priming is essential for the effect of progesterone upon MR mRNA in vivo. Further, they suggest the possibility of heterologous regulation of corticosteroid receptors in the brain, whereby the responsiveness of the limbic-hypothalamo-pituitary-adrenal system to corticosteroids may be modulated.

Adrenal Glands↗

PubMed1996

Regulation of estrogen sulfotransferase in human endometrial adenocarcinoma cells by progesterone.

During the secretory phase of the human menstrual cycle, the endometrium is minimally responsive to the estrogens secreted from the ovaries. Conjugation of beta-estradiol (E2) with sulfate is thought to be an important mechanism in the regulation of the levels of active E2 in endometrial tissue. Estrogen sulfation is reportedly increased during the secretory phase in response to the high levels of progesterone secreted by the ovaries. Estrogen sulfotransferase (hEST), a distinct form of human cytosolic sulfotransferase (ST) with an affinity for E2 and estrone at low nanomolar concentrations, has recently been cloned and expressed in mammalian cells and in bacteria (J Steroid Biochem Mol Biol 52:529, 1995). At least two other forms of human cytosolic ST, dehydroepiandrosterone ST (hDHEA-ST) and the phenol-sulfating form of phenol-ST (hP-PST), also conjugate estrogens but at micromolar concentrations. This report describes the specific induction of hEST in human Ishikawa endometrial adenocarcinoma cells by progesterone as a model for the increases in estrogen sulfation observed in women during the secretory phase of the menstrual cycle. Treatment of Ishikawa cells with 10 microns progesterone for 48 h resulted in a 7-fold increase in the sulfation of 20 nM E2. The sulfation of selective substrates for human dehydroepiandrosterone sulfotransferase (hDHEA-ST) and the two forms of phenol sulfotransferase (hP-PST, hM-PST) were not affected by treatment with progesterone. The levels of immunoreactive hEST and hEST mRNA in the Ishikawa cells were both increased by progesterone, whereas the levels of immunoreactive hDHEA-ST, hP-PST, and hM-PST were not altered. hEST activity was not induced by treatment of Ishikawa cells with varying concentrations of E2, testosterone, or cortisol. The induction of hEST by progesterone was inhibited by RU-486, indicating that progesterone is acting via the progesterone receptor. These results indicate that progesterone is capable of specifically inducing hEST and estrogen sulfation in human Ishikawa adenocarcinoma cells and suggest a mechanism for increasing estrogen sulfation in the endometrium during the secretory phase of the menstrual cycle.

Adenocarcinoma↗

PubMed2001

Role of endogenous opioid peptides in mediating progesterone-induced disruption of the activation and transmission stages of the GnRH surge induction process.

How progesterone blocks the E2-induced GnRH surge in females is not known. In this study we assessed whether the endogenous opioid peptides (EOPs) that mediate progesterone negative feedback on pulsatile GnRH secretion also mediate the blockade of the GnRH surge. We treated ovariectomized ewes with physiological levels of E2 and progesterone to stimulate and block the GnRH surge, respectively, using LH secretion as an index of GnRH release. A pilot study confirmed that blocking opioidergic neurotransmission with the opioid receptor antagonist, naloxone (NAL; 1 mg/kg.h, i.v.), could prevent the suppression of pulsatile LH secretion by progesterone in our model. By contrast, antagonizing EOP receptors with NAL did not restore LH surges in ewes in which the E2-induced GnRH surge was blocked by progesterone treatment during the E2-dependent activation stage (Exp 1) of the GnRH surge induction process. However, in ewes treated with progesterone during the E2-independent transmission stage (Exp 2), NAL partially restored blocked LH surges, as indicated by increased fluctuations in LH that, in some cases, resembled LH surges. We conclude, therefore, that the EOPs that mediate progesterone negative feedback on pulsatile GnRH secretion are not involved in blockade of activation of the E2-induced GnRH surge by progesterone, but do appear to be part of the mechanism by which progesterone disrupts the transmission stage.

Animals↗

PubMed2003

The role of mitogen-activated protein kinase in insulin and insulin-like growth factor I (IGF-I) signaling cascades for progesterone and IGF-binding protein-1 production in human granulosa cells.

Insulin and IGF-I participate in the regulation of ovulation, steroidogenesis, and IGF-binding protein (IGFBP) production in the ovary. Insulin and IGF-I actions in the ovary are closely related. For example, insulin may amplify IGF-I action in the ovary by up-regulating type I IGF receptors and inhibiting IGFBP-1 production, thus increasing the bioavailability of IGF-I. It is hypothesized that ovarian effects of insulin in insulin-resistant states are mediated via an insulin action pathway(s) distinct from those involved in glucose transport. We previously reported that insulin-induced stimulation of progesterone and inhibition of IGFBP-1 production in the human ovary are mediated by signaling pathways that are independent of phosphatidylinositol 3-kinase, the enzyme whose activation is crucial for glucose transport. We now examined whether activation of MAPK is necessary to mediate insulin-induced or IGF-I-induced stimulation of progesterone or inhibition of IGFBP-1 production in human granulosa cells. Human granulosa cells were obtained during in vitro fertilization. Cells (0.5-1 x 10(5)) were incubated for 24 h in the presence of 0, 10, 10(2), or 10(3) ng/ml insulin or 0, 0.5, 1, 2.5, or 5 ng/ml IGF-I and in the presence or absence of 1 micro M PD98059, a specific inhibitor of ERK1/2 MAPK. The progesterone concentration in the tissue culture medium was measured by RIA (Pantex, Santa Monica, CA), and the IGFBP-1 concentration was measured by immunoradiometric assay (DSL-7800, Diagnostic Systems Laboratories, Inc., Webster, TX). MAPK activity was assessed using the MAPK IP-Kinase assay kit (Upstate Biotechnology, Inc., Lake Placid, NY). ANOVA was used to compare mean values of progesterone or IGFBP-1 concentrations. MAPK was stimulated by insulin up to 350% of the baseline value. Progesterone production in human granulosa cells was stimulated by insulin in a dose-related manner to 123% of the control value (P < 0.001), and IGFBP-1 production was inhibited to 25% of the baseline value (P < 0.001). Despite inhibiting MAPK activity by 99%, PD98059 (1 micro M) did not interfere with insulin-induced stimulation of progesterone or inhibition of IGFBP-1 production. MAPK was stimulated by IGF-I to 730% of the baseline value, with maximal stimulation achieved at 0.5 ng/ml IGF-I. Progesterone production in granulosa cells was stimulated by IGF-I to 130% of the control value (P < 0.001), whereas IGFBP-1 production was inhibited to 44% of the control value (P < 0.001). PD98059 (1 micro M) inhibited IGF-I-induced MAPK activity by 94%. In the presence of 1 micro M PD98059, IGF-I-induced stimulation of progesterone production was inhibited by 96% (P < 0.001). The inhibitory effect of IGF-I on IGFBP-1 production was reduced in the presence of 1 micro M PD98059 by 45% at 5 ng/ml IGF-I and was completely abolished in the presence of 1 micro M PD98059 at concentrations of IGF-I ranging from 0.5-2.5 ng/ml (P < 0.001). We conclude that, under conditions of our experiments, insulin-induced stimulation of progesterone or inhibition of IGFBP-1 production in human granulosa cells does not require MAPK activation, whereas similar effects of IGF-I are largely MAPK dependent.

Cells, Cultured↗

PubMed1978

The relationships between serum concentrations of 17OH-progesterone and other serum and urinary steroids in patients with congenital adrenal hyperplasia.

Simultaneous determinations of serum concentrations of 17OH-progesterone, testosterone, androstenedione, and progesterone, and of urinary excretion of 17-ketosteroids and pregnanetriol have been performed at intervals in 31 patients with the C21-hydroxylase form of congenital adrenal hyperplasia. In prepubertal patients there were highly significant correlations between levels of 17OH-progesterone and those of testosterone, androstenedione, and progesterone, respectively. Similar correlations were observed in adolescent girls. In adolescent boys rising 17OH-progesterone levels were reflected by increasing levels of androstenedione and progesterone, but there was no change in serum testosterone concentrations. Levels of serum 17OH-progesterone below 200 ng/dl were uniformly associated with normal serum concentrations of testosterone, androstenedione, and progesterone, and normal urinary 17-ketosteroid and pregnanetriol excretion. In contrast, levels above 1000 ng/dl were accompanied by increased levels of the other steroids except in adolescent males; in this group the finding of unchanging serum testosterone concentrations in spite of rising 17OH-progesterone levels presumably indicates that testosterone of adrenal origin causes suppression of testicular testosterone production, either through a direct effect upon Leydig cells or via suppression of LH release.

17-Ketosteroids↗

PubMed1981

Progesterone positive feedback on gonadotropin release in estrogen-primed postmenopausal women: central nervous system and pituitary as possible sites of action.

To investigate the site and mode of action of progesterone in inducing gonadotropin release, the effects of catecholamine-depleting (methyldopa) or dopamine agonist (bromocriptine) drugs on progesterone positive feedback and the gonadotropin response to a centrally acting noradrenergic drug (clonidine) were evaluated in estrogen-primed postmenopausal women. Progesterone administration induced a significant rise in LH, FSH, and PRL serum levels in the control group. Bromocriptine administration was followed by a marked suppression of PRL release but did not modify the gonadotropin response to progesterone. Methyldopa pretreatment significantly reduced the progesterone-induced LH surge, while PRL release was unaffected. After estrogen priming, clonidine administration did not result in an increase in serum LH or FSH concentrations. The dissociated responses of LH and PRL in bromocriptine-pretreated subjects and the significant reduction of the LH rise after progesterone in methyldopa-pretreated women seem to invalidate the hypothesis that a fall in endogenous dopamine is responsible for progesterone positive feedback and suggest that neural noradrenergic mechanisms are involved in progesterone-induced gonadotropin release. The ineffectiveness of a centrally acting noradrenergic agonist in inducing gonadotropin rise provides indirect evidence that an increased pituitary responsiveness may also be involved in progesterone positive feedback.

Aged↗