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Results for “PROGESTERONE”

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At least 19 recordsLinked to original sources

PubMed2000

Effect of sequential transdermal progesterone cream on endometrium, bleeding pattern, and plasma progesterone and salivary progesterone levels in postmenopausal women.

BACKGROUND: Transdermal progesterone is being used in some countries as a purported treatment for menopausal symptoms, either alone or prescribed in conjunction with estrogen, but little information exists regarding the biological activity and effectiveness of this method of delivery of progesterone in protecting the endometrium from excess proliferation. This study was designed to evaluate the use of sequential transdermal progesterone. End-points evaluated included endometrial cellular response and bleeding pattern as well as plasma hormone levels and salivary progesterone estimations. METHOD: Twenty-seven postmenopausal women were treated with continuous transdermal estrogen (28-day cycle) and a cream containing 16, 32 or 64 mg of progesterone in each 4-cm extrusion from a tube of Pro-Feme administered daily in a sequential (days 15-28 of cycle) regimen. Blood and endometrial samples were analyzed for progesterone response prior to therapy, after the first 14 days of unopposed transdermal estrogen and following 14 days of transdermal progesterone. Saliva samples were taken during the last 14 days of the 84-day study, when the final progesterone cream therapy was being applied. RESULTS: Hormone assay indicated that physiological levels of estradiol were achieved, but progesterone levels were insufficient to induce any detectable change in the endometrium. Only one patient experienced bleeding during the study period. Levels of salivary progesterone were so variable as to be considered completely unreliable in determining the potential influence on biological activity. INTERPRETATION: Pro-Feme transdermal progesterone administered in a 16-, 32- or 64-mg daily dose for 14 days in a sequential regimen does not appear to be effective in inducing a secretory change in a proliferative endometrium. Salivary progesterone levels were not of value in managing the therapy of postmenopausal women.

Administration, Cutaneous↗

PubMed1991

Inhibition of uterine contractility by progesterone and progesterone metabolites: mediation by progesterone and gamma amino butyric acidA receptor systems.

Progesterone and several progesterone metabolites are capable of inhibiting uterine contractility. Some progesterone metabolites have shown little or no affinity for the progesterone receptor but have been found to be potent modulators of the GABAA receptor system. This study examined whether the inhibition of uterine contraction by progesterone and its metabolites was progesterone receptor-mediated or gamma amino butyric acidA (GABAA) receptor-mediated. Uterine contractions were measured in annular rings of uterine tissue, 5 mm in length, from diestrous II rats, under a fixed tension of 1 gram. The steroids tested were 3 beta-hydroxy-5 beta-pregnan-20-one (6 micrograms/ml), 5 beta-pregnane-3,20-dione (10 micrograms/ml), 3 alpha-hydroxy-5 alpha-pregnan- 20-one (3 alpha,5 alpha-THP, 27.5 micrograms/ml), and progesterone (40 micrograms/ml). All compounds significantly inhibited spontaneous uterine contractions when compared to controls. No effect was seen by either 16 micrograms/ml of the progesterone antagonist, RU486, or 32 micrograms/ml of the GABAA antagonist, pictrotoxin, when administered alone. However, when uterine tissues were exposed to a combination of the steroid and the antagonist, the effect of 3 beta-hydroxy-5 beta-pregnan-20-one and 3 alpha,5 alpha-THP was blocked by picrotoxin but not by RU486, indicating that the action of these steroids was mediated through the GABAA system. The effect of 5 beta-pregnane-3,20-dione and progesterone was effectively blocked by RU486 but not by picrotoxin, suggesting that their actions were mediated through the progesterone receptor system. These results indicate that multiple mechanisms exist in the uterus for inhibiting uterine contractility by progesterone and its metabolites.

5-alpha-Dihydroprogesterone↗

PubMed2003

Effects of injury and progesterone treatment on progesterone receptor and progesterone binding protein 25-Dx expression in the rat spinal cord.

Progesterone provides neuroprotection after spinal cord injury, but the molecular mechanisms involved in this effect are not completely understood. In this work, expression of two binding proteins for progesterone was studied in intact and injured rat spinal cord: the classical intracellular progesterone receptor (PR) and 25-Dx, a recently discovered progesterone membrane binding site. RT-PCR was employed to determine their relative mRNA levels, whereas cellular localization and relative protein levels were investigated by immunocytochemistry. We observed that spinal cord PR mRNA was not up-regulated by estrogen in contrast to what is observed in many brain areas and in the uterus, but was abundant as it amounted to a third of that measured in the estradiol-stimulated uterus. In male rats with complete spinal cord transection, levels of PR mRNA were significantly decreased, while those of 25-Dx mRNA remained unchanged with respect to control animals. When spinal cord-injured animals received progesterone treatment during 72 h, PR mRNA levels were not affected and remained low, whereas 25-Dx mRNA levels were significantly increased. Immunostaining of PR showed its intracellular localization in both neurons and glial cells, whereas 25-Dx immunoreactivity was localized to cell membranes of dorsal horn and central canal neurons. As the two binding proteins for progesterone differ with respect to their response to lesion, their regulation by progesterone, their cellular and subcellular localizations, their functions may differ under normal and pathological conditions. These observations point to a novel and potentially important role of the progesterone binding protein 25-Dx after injury of the nervous system and suggest that the neuroprotective effects of progesterone may not necessarily be mediated by the classical progesterone receptor but may involve distinct membrane binding sites.

Animals↗

PubMed1978

Progesterone in the uterus. X. Dependence of the in vitro progesterone metabolism on progesterone binding in rat uterus.

The effect of estrogen pretreatment was stud-ed on the in vitro metabolism and binding of progesterone in uteri of ovariectomized rats in order to prove the dependence of the metabolism of progesterone on its binding. For this purpose, the extent of progesterone binding was varied in uterine tissue by different estrogen treatment of the rats and compared with the metabolism under the same conditions. The protein content determined in 100 mg tissue was used as parameter indicating the success of the pretreatment. Estrogen exposure of the rats for 30 or 45 hrs. caused a rise of protein amount in uterine tissue which was accompanied by an increase of binding sites of progesterone binding components. The binding sites were determined by charcoal adsorption technique and SCATCHARD-analysis. Under nearly the same success of estrogen pretreatment, the increase of the portein amount and with it the rise of binding sites reduced the amount of progesterone metabolites in uterine tissue. The metabolites were determined by quantitative TLC-analysis of the recovered compounds from uterine segments after incubation with radioactive progesterone. Additionally, an enlarged metabolic rate could be observed after saturation of binding components. It is concluded from the results of these experiments that progesterone binding components are factors limiting the enzymatic conversion of progesterone in rat uterus.

Animals↗

PubMed1981

Concentration and relationship to progesterone of progesterone-binding globulin in pregnant guinea-pigs: measurement by progesterone tracer binding assay.

A single-point progesterone tracer binding assay (TBA) was developed to measure the concentration of progesterone-binding globulin (PBG) in the serum of pregnant guinea-pigs. Tritiated progesterone was added to dilutions of a reference serum, the percentage bound calculated and a standard curve constructed. The amount of progesterone tracer bound to serum samples was determined, and the concentration of binding protein in the sample relative to the reference was calculated. The molar concentration in the reference serum was determined by Scatchard analysis. The TBA could readily process 30 samples per day. There was a rapid rise in PBG concentrations between days 15 and 20 of gestation, in parallel with progesterone concentrations. The molar ratio of PBG: progesterone was approximately 10:1 after this time, until about day 45 when there was an increase in ratio.

Alpha-Globulins↗

PubMed2000

Progesterone and follicular changes in postpartum noncyclic dairy cows after treatment with progesterone and estradiol or with progesterone, GnRH, PGF2alpha, and estradiol.

A previous study showed that noncyclic dairy cows treated with 10 microg of GnRH and a progesterone-releasing CIDR insert on Day 0, 25 mg of PGF2alpha and CIDR removal on Day 7, followed by 1 mg estradiol benzoate on Day 9 for those cows that still had not shown estrus (CGPE program) had higher conception rate (47% vs. 29%) than cows treated only with CIDR and estradiol benzoate as above (CE program). This study was to investigate the mechanisms by which the CGPE program improved conception rate compared with the CE program. Sixteen noncyclic Holstein-Friesian cows were randomly assigned to 2 groups balanced for the size and growth pattern of the dominant follicles, which were determined by ultrasonography over a 3-d period. One group received the above CGPE treatment, and the other group received the CE treatment. Follicular and luteal development were monitored by daily ultrasonography. Blood samples were collected daily from Day -2 to Day 11, and thereafter milk samples were collected thrice weekly for a further 24 d. Blood and milk samples were analyzed for progesterone. The GnRH treatment induced ovulation in 7 of 8 cows, resulting in elevated (P<0.05) progesterone concentrations between Days 4 and 7 for cows in the CGPE group. All induced CL underwent luteolysis by 24 h after PGF2alpha treatment. Within 5 d of CIDR removal, 7 of 8 cows in both the CE and CGPE groups ovulated. The interval from emergence of the ovulatory follicle to ovulation was similar (P=0.32) but less (P<0.05) variable for the CGPE group (9.0+/-0.3 d) compared with the CE group (10.3+/-1.2 d). Progesterone concentration in milk samples was similar between the two groups up to 10 d after ovulation. In summary, the GnRH treatment induced ovulation or turnover of dominant follicles, induced a synchronized initiation of a new follicular wave, and increased the progesterone concentration from 4 d after treatment. These could be the reasons for the increased conception rate of cows treated with the CGPE program.

Animals↗

PubMed1975

Progesterone in the uterus. IV. Dependence of the in vitro progesterone metabolism in the rat uterus on the progesterone concentration.

After incubation of uterine segments of normal rats with various 3H-progesterone concentrations in nutrient medium, different patterns of radioactive steroids were obtained in uterine tissue. Using hormone concentrations of less than 5 X 10(-7)M progesterone metabolites could not be detected in the tissue. A series of metabolites appeared with progesterone concentrations of 10(-6)M and higher. Six radiometabolites were identified and two were characterized.

Animals↗

PubMed1975

Effect of exogenous progesterone on its endogenous levels: biological half-life of progesterone and lack of progesterone binding in mares.

The disappearance rate of progesterone from blood plasma of an ovariectomized mare was rapid and occurred in three phases. The half-life of the first component was 2-5 min and that of the second was 20 min; the half-life of the much slower third component was not measured. Progesterone, administered to ovariectomized and deeply anoestrous mares at the rate of 150 or 300 mg/day, maintained maximal peripheral levels of 6 to 8 ng/ml. Physiological levels were reached in 21 days using a dose of 150 mg and in 11 days with 300 mg daily. After withdrawal, circulating levels dropped rapidly. Blood plasma of mares appears to lack progesterone-specific binding proteins. It is concluded that the problem of habitual abortion and its treatment in mares need re-evaluation.

Animals↗

PubMed1975

Progesterone in the uterus. V. Correlation of the in vitro progesterone metabolism with the progesterone binding in rat uterus.

Incubations of rat uterine segments with varying 3H-progesterone concentrations were performed to study the hormone uptake by the tissue. The radioactivity of the uterus and the nutrient medium were plotted in form of a SCATCHARD plot. Additionally, the binding capacity of the uterine cytosol was measured. In both systems, the hormone was found to be associated with two components which differ from each other in their association constants. The progesterone metabolism occuring at a hormone concentration of 10(-6)M and more in the incubation medium is discussed with respect to the affinity and the capacity of the hormone binding components.

Animals↗

PubMed1999

Progesterone metabolism in the human kidney and inhibition of 11beta-hydroxysteroid dehydrogenase type 2 by progesterone and its metabolites.

Progesterone binds with high affinity to the mineralocorticoid (MC) receptor, but confers only very low agonistic MC activity. Therefore, progesterone is a potent MC antagonist in vitro. Although progesterone reaches up to 100 times higher plasma levels in late pregnancy than aldosterone, the in vivo MC antagonistic effect of progesterone seems to be relatively weak. One explanation for this phenomenon could be local metabolism of progesterone in the human kidney, similar to the inactivation of cortisol to cortisone by the 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 2. We studied the metabolism of progesterone in the human kidney in vitro and found reduction to 20alpha-dihydro (DH)-progesterone as the main metabolite. Ring-A reduction to 5alpha-DH-progesterone, 20alpha-DH-5alpha-DH-progesterone, and 3beta,5alpha-tetrahydro (TH)-progesterone was also documented. We further showed for the first time that 17-hydroxylation of progesterone (17alpha-OH-progesterone, 17alpha-OH, 20alpha-DH-progesterone), normally localized in the adrenals and the gonads, occurs in the human adult kidney. We found no formation of deoxycorticosterone from progesterone in the human adult kidney. Using human kidney cortex microsomes, we tested the inhibitory potency of progesterone and its metabolites on the 11beta-HSD type 2. The most potent inhibitor was progesterone itself (IC50 = 4.8 x 10(-8) mol/L), followed by 5alpha-DH-progesterone (IC50 = 2.4 x 10(-7) mol/L), 20alpha-DH-progesterone, 3beta,5alpha-TH-progesterone, 17alpha-OH-progesterone, and 20alpha-DH-5alpha-DH-progesterone (IC50 between 7.7 x 10(-7) mol/L and 1.3 x 10(-6) mol/L). The least potent inhibitor was 17alpha-OH,20alpha-DH-progesterone. In addition to progesterone metabolism by the kidney, the inhibition of 11beta-HSD type 2 by progesterone and its metabolites could be a second explanation for the weak MC-antagonist activity of progesterone in vivo. Inhibition of 11beta-HSD type 2 leads to an increase of intracellular cortisol in a way that the local equilibrium between the MC agonist cortisol and the antagonist progesterone is shifted to the agonist side.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1992

Serum progesterone and 17-hydroxyprogesterone in the diagnosis of ectopic pregnancies and the value of progesterone replacement in intrauterine pregnancies when serum progesterone levels are low.

The corpus luteum function was evaluated in patients with surgically confirmed ectopic pregnancy (EP) in a multicenter study. In addition, the minimal threshold of serum progesterone (P) concentration required for salvaging intrauterine pregnancies (IUP) was also examined. Results show that single P or 17-OHP measurements are not diagnostic for EP, since mean P levels in EP were similar to those with spontaneous abortion though significantly lower than those in controls. 17-OHP levels in EP overlapped in 50% with IUP, and the mean levels were significantly lower only at 6-7 weeks. The 17-OHP levels when compared to hCG supports the view that corpus luteum defect is primary. In IUP, P levels < 8 ng/ml still were associated with viable (60%) pregnancy; thus no minimal threshold could be established.

17-alpha-Hydroxyprogesterone↗

PubMed2000

Preserved forearm endothelial responses with acute exposure to progesterone: A randomized cross-over trial of 17-beta estradiol, progesterone, and 17-beta estradiol with progesterone in healthy menopausal women.

Regularly menstruating women are relatively protected from cardiovascular disease. Epidemiological and endothelial function studies attribute this protection to estradiol (E(2)), but both progesterone (P) and E(2) are normally present. A range of vascular effects of added progestins have been described, from neutral to detrimental, but the effects of P per se on endothelial function in humans have not been reported. We therefore investigated the acute effects of E(2), P, and E(2) combined with P, on endothelium-dependent and -independent forearm blood flow responses. Using venous occlusion plethysmography, forearm blood flow (FBF) was measured during acute brachial artery infusions, achieving physiologic levels of 17-beta-E(2), P, and 17-beta-E(2) with P in healthy menopausal women with no cardiovascular disease risk factors. Vehicle or hormones were infused, in random order, on 4 days, 1 week apart. Flow responses were measured during coinfusions of hormone with the endothelium-dependent vasodilator acetylcholine and the endothelium-independent vasodilator sodium nitroprusside. Twenty-seven healthy menopausal women were studied, and all had normal baseline endothelial responses. Small ( approximately 15%), statistically nonsignificant increases in endothelium-dependent flow responses were seen after all acute hormone treatments. No impairment in response was seen with P alone or in combination with 17-beta-E(2). In healthy menopausal women without cardiovascular disease risk factors and without baseline defects in endothelial function, acute exposure to physiologic levels of 17-beta-E(2), P, and 17-beta-E(2) with P produced equivalent endothelium-dependent responses. These data suggest that P does not have detrimental vascular effects in humans.

Cross-Over Studies↗

PubMed1996

Intrahypothalamic implantation of progesterone in castrated male whiptail lizards (Cnemidophorus inornatus) elicits courtship and copulatory behavior and affects androgen receptor- and progesterone receptor-mRNA expression in the brain.

A primary tenet of behavioral neuroendocrinology is that gonadal steroid hormones act on limbic nuclei to activate mating behavior in vertebrates. Traditionally, research has focused on the regulation of male-typical sexual behavior by testicular androgens and female-typical sexual behavior by ovarian estrogen and progesterone. Indeed, progesterone generally is regarded as an antiandrogen, acting centrally to inhibit sexual behavior in males. However, experiments with lizards, and more recently with rats, have challenged this paradigm. For example, exogenous progesterone induces mating behavior in some, but not all, castrated male whiptail lizards. The present study determined that implantation of progesterone into the anterior hypothalamus preoptic area of castrated, progesterone-sensitive males completely restored sexual behavior but failed to elicit sexual activity in castrated, progesterone-insensitive males. Further, androgen receptor -and progesterone receptor-mRNA expression in specific brain regions was significantly different in progesterone-sensitive versus progesterone-insensitive animals. Progesterone-sensitive males showed significantly higher relative abundance of androgen receptor-mRNA in the preoptic area, amygdala, and lateral septum, as compared with progesterone-insensitive animals receiving the same treatment. In contrast, progesterone receptor-mRNA abundance was lower in preoptic area of progesterone-sensitive males than in progesterone-insensitive males. No differences were found in the baseline abundance of androgen receptor-or progesterone receptor-mRNA in these nuclei between control groups of progesterone-sensitive and progesterone-insensitive males who were castrated but not implanted. This suggests that progesterone differentially regulates its own receptor as well as androgen receptor in areas of the brain involved in the control of sexual behavior of males and that the nature of this regulation shows individual variability.

Amygdala↗

PubMed1983

[Effect of adrenocorticotropin on progesterone, 20alpha-OH- progesterone and adenosine 3',5'-monophosphate in isolated luteal cells from rat ovaries].

The present investigation was designed to study the effect of synthetic ACTH on the synthesis of progesterone, 20 alpha-OH-progesterone and adenosine-3', 5'-monophosphate (cAMP) in isolated luteal cells. Experiments were conducted on rats from three groups. Group I: PMS primed immature rats. Group II: PMS plus hCG primed immature rats. Group III: pregnant rats. Luteal cells were isolated by the Kumai Method (7) using a sucrose density gradient after digestion with trypsin and collagenase. Luteal cells were divided into three fractions; S-1, S-2 and S-3. Following an 18 hr-incubation of S-1 cells of day 7 after PMS injection, a significant increase in progesterone release by ACTH lasted from 6 to 18 hr, whereas 20 alpha-OH-progesterone decreased significantly by ACTH from 8 to 18 hr. There were no differences in progesterone and 20 alpha-OH-progesterone releases from S-2 cells of day 7 between media with and without ACTH. Progesterone release without ACTH reached the peak on day 7 in Group I and on day 6 in Group II. ACTH stimulated progesterone and inhibited 20 alpha-OH-progesterone releases in Groups I and II. The maximum effect of ACTH in both Groups was noted on days 6 and 7. There were no differences in the Effective Dose (ED50) and the Inhibitory Dose (ID50) of ACTH between Group I and Group II. In Group III, releases of progesterone and 20 alpha-OH-progesterone from S-1 cells to media with or without ACTH decreased remarkably after 11 days of gestation. On days, 3, 5 and 8 of gestation, a significant increase in progesterone release from S-1 cells was noted by the ACTH addition. 20 alpha-OH-progesterone release from S-1 cells to media with or without ACTH decreased as the pregnancy advanced. Total cAMP of intra- and extra-cellular S-1 cells (Group II) on day 5 after PMS injection was assayed. ACTH induced an increase in intracellular cAMP. The present results indicate the following: (1) In Group I and Group II, progesterone release increased with the age of the luteal cells and ACTH dose. In Group III, ACTH stimulated progesterone release in a dose-dependent manner in early gestation. (2) 20 alpha-OH-progesterone release decreased by ACTH dose in Group I and Group II, and decreased in Group III as the gestation advanced. (3) Intracellular cAMP increased by ACTH in Group II.

20-alpha-Dihydroprogesterone↗

PubMed1992

Changes of progesterone content of rat uterine flushings in relation to serum concentrations of progesterone during the oestrous cycle.

Uterine fluid was collected from four-day cyclic rats at each stage of the oestrous cycle and assayed for progesterone and protein content. Progesterone was determined by radioimmunoassay either after ethanol (or 2.5% NaOH) denaturation of proteins from uterine flushings ('total' progesterone) or without protein denaturation ('ether-extractable' progesterone). The amount of 'ether-extractable' progesterone in the lumen was constant from metoestrus to pro-oestrus (340 pg per uterus) but lower in oestrus (200 pg per uterus). However, 'total' progesterone content of uterine fluid was subject to cyclic variations and was highest in dioestrus (890 pg per uterus) and lowest in oestrus (350 pg per uterus), in contrast to serum progesterone which is lowest in dioestrus and highest in oestrus. Protein content of uterine flushings peaked to 780 micrograms per uterus in pro-oestrus then fell to about 140 micrograms per uterus until the end of the oestrous cycle. Changes in protein content of the lumen were followed by qualitative variations since the mean amount of 'bound' progesterone ('total' progesterone minus 'ether-extractable' progesterone) released per milligram of denatured lumen protein rose from 1.8 pmol in pro-oestrus to 18.2 pmol in dioestrus. The changes of luminal 'bound' progesterone during the oestrous cycle suggest that progesterone binding to luminal proteins could be an important modulator of progesterone action in rat uterus. Moreover, the variations in progesterone content of the lumen, irrespective of serum progesterone concentrations, are consistent with the hypothesis that progesterone synthesis occurs in the uterus.

Animals↗

PubMed1990

The nuclear conversion of pregnenolone to progesterone and subsequent binding to the nuclear progesterone-binding protein in the guinea pig adrenal cortex: a possible regulatory role for the pregnenolone-binding protein.

Progesterone, which is normally produced in the endoplasmic reticulum, was found to be rapidly degraded in the cytosolic fraction of the guinea pig adrenal cortex in vitro. Assuming this finding reflects what happens in vivo raises a question as to the source of progesterone for interacting with a nuclear progesterone-binding protein (P4-BP) that exists in this model system. It was subsequently found that pregnenolone, which in contrast to progesterone is relatively stable in the cytosol, was converted to progesterone by endogenous nuclear 3 beta-ol dehydrogenase. It was also determined that the nuclear-derived progesterone specifically bound to the nuclear P4-BP which is distinct from the classical progesterone receptor. The guinea pig adrenocortical cytosol contains a specific pregnenolone-binding protein (P5-BP) that could be virtue of its pregnenolone binding activity regulate the conversion of pregnenolone to progesterone in the nuclear compartment and thereby reduce the binding of progesterone to the nuclear P4-BP. A partially purified P5-BP preparation markedly inhibited the nuclear conversion of pregnenolone to progesterone and reduced the binding of progesterone to the nuclear P4-BP (P5-BP did not directly inhibit binding of progesterone to the nuclear P4-BP). The ability of P5-BP to inhibit the conversion of pregnenolone to progesterone was destroyed by heat and alkaline phosphatase treatment. The binding of pregnenolone to the P5-BP, as previously reported, is regulated by phosphorylation/dephosphorylation, and alkaline phosphatase-treated P5-BP loses the ability to bind pregnenolone; this process can be reversed by a cytosolic kinase. This provides a mechanism for controlled release of bound steroid. These results suggest that P5-BP regulates the nuclear conversion of pregnenolone to progesterone and thus the binding of progesterone to the nuclear P4-BP.

Adrenal Cortex↗

PubMed2000

Progesterone regulation of the progesterone receptor in rat gonadotropes.

For rat pituitary cells, progesterone receptor (PR) protein localizes to gonadotropes and PR messenger RNA is induced by E2 and rapidly but transiently down-regulated by progesterone. Here we quantitatively establish the down-regulatory effect of progesterone on PR protein and evaluate possible mechanisms. Nuclear PR-immunoreactivity (PR-IR) in gonadotropes, identified by dual immunofluorescence, was analyzed by quantitative confocal microscopy. Pituitary cells from female rats were cultured +/- 0.2 nM E2 for 3 days. We confirmed the E2 requirement for PR induction in gonadotropes and determined that the increase in PR-IR required about 24 h. After removal of E2, PR-IR decreases were not found until 24-36 h. Addition of progesterone (40 nM) to E2-treated cells led to a dramatic loss in PR-IR by 9 h (26% of control); by 24 h, PR-IR was barely detectable. Reappearance of nuclear PR-IR required progesterone removal (8-fold increase by 12 h after progesterone removal) and protein synthesis (cycloheximide inhibited the reappearance of PR-IR). Although progesterone decreased PR-IR whether or not E2 was present concurrent with progesterone, the recovery of PR-IR required E2. RU486 completely blocked progesterone-induced PR down-regulation. Because the sustained progesterone-induced loss of PR protein did not correlate with previously reported temporal changes in PR messenger RNA levels, we examined a role for protein degradation. When cells were coincubated with progesterone and the proteasome inhibitor, MG132 (1 microM), the expected decrease in PR protein was abrogated. In summary, progesterone leads to a rapid and extensive reduction in nuclear PR protein in gonadotropes. The progesterone-dependent down-regulation of PR occurs, at least in part, by a proteasome-mediated pathway. Recovery of PR protein requires removal of progesterone, the presence of E2, and protein synthesis. These dynamic changes in nuclear PR levels coincide with the temporal extent of the preovulatory LH surge in rats and could provide a basis for progesterone's biphasic action on LH secretion.

Animals↗

PubMed1996

Regulation of oxytocin, oestradiol and progesterone receptor concentrations in different uterine regions by oestradiol, progesterone and oxytocin in ovariectomized ewes.

The regulation of oxytocin, oestradiol and progesterone receptors in different uterine cell types was studied in ovariectomized ewes. Animals were pretreated with a progestogen sponge for 10 days followed by 2 days of high-dose oestradiol to simulate oestrus. They then received either low-dose oestradiol (Group E), low-dose oestradiol plus progesterone (Group P) or low-dose oestradiol, progesterone and oxytocin (via osmotic minipump; Group OT). Animals (three to six per time-point) were killed following ovariectomy (Group OVX), at oestrus (Group O) or following 8, 10, 12 or 14 days of E, P or OT treatment. In a final group, oxytocin was withdrawn on day 12 and ewes were killed on day 14 (Group OTW). Oxytocin receptor concentrations and localization in the endometrium and myometrium were measured by radioreceptor assay, in situ hybridization and autoradiography with the iodinated oxytocin receptor antagonist d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]-vasotocin. Oestradiol and progesterone receptors were localized by immunocytochemistry. Oxytocin receptors were present in the luminal epithelium and superficial glands of ovariectomized ewes. In Group O, endometrial oxytocin receptor concentrations were high (1346 +/- 379 fmol [3H]oxytocin bound mg protein-1) and receptors were also located in the deep glands and caruncular stroma in a pattern resembling that found at natural oestrus. Continuing low-dose oestradiol was unable to sustain high endometrial oxytocin receptor concentrations with values decreasing significantly to 140 +/- 20 fmol mg protein-1 (P < 0.01), localized to the luminal epithelium and caruncular stroma but not the glands. Progesterone treatment initially abolished all oxytocin receptors with none present on days 8 or 10. They reappeared in the luminal epithelium only between days 12 and 14 to give an overall concentration of 306 +/- 50 fmol mg protein-1. Oxytocin treatment caused a small increase in oxytocin receptor concentration in the luminal epithelium on days 8 and 10 (20 +/- 4 in Group P and 107 +/- 35 fmol mg protein-1 in Group OT, P < 0.01) but the rise on day 14 was not affected (267 +/- 82 in Group OT and 411 +/- 120 fmol mg protein-1 in Group OTW). In contrast, oestradiol treatment was able to sustain myometrial oxytocin receptors (635 +/- 277 fmol mg protein-1 in Group O and 255 +/- 36 in Group E) and there was no increase over time in Groups P, OT and OTW with values of 61 +/- 18, 88 +/- 53 and 114 +/- 76 fmol mg protein-1 respectively (combined values for days 8-14). Oestradiol receptor concentrations were high in all uterine regions in Group O. This pattern and concentration was maintained in Group E. In all progesterone-treated ewes, oestradiol receptor concentrations were lower in all regions at all time-points. The only time-related change occurred in the luminal epithelium in which oestradiol receptors were undetectable on day 8 but developed by day 10 of progesterone treatment. Progesterone receptors were present at moderate concentrations in the deep glands, caruncular stroma, deep stroma and myometrium in Group O. Oestradiol increased progesterone receptors in the luminal epithelium, superficial glands, deep stroma and myometrium. Progesterone caused the loss of its own receptor from the luminal epithelium and superficial glands and decreased its receptor concentration in the deep stroma and myometrium at all time-points. There was a time-related loss of progesterone receptors from the deep glands of progesterone-treated ewes between days 8 and 14. These results show differences in the regulation of receptors between uterine regions. In particular loss of the negative inhibition by progesterone on the oxytocin receptor by day 14 occurred only in the luminal epithelium, but is unlikely to be a direct effect of progesterone as no progesterone receptors were present on luminal epithelial cells between days 8 and 14.

Animals↗