Luteinizing Hormone Induction Research Articles

HDAC1 in the Ovarian Granulosa Cells of Tan Sheep Improves Cumulus Cell Expansion and Oocyte Maturation Independently of the EGF-like Growth Factors.

Simple SummaryThis study aimed to explore the possible role of histone deacetylase 1 (HDAC1), an epigenetic modifying enzyme, in the improvement of oocyte maturation recovered from the Tan sheep of China. We supplemented a specific inhibitor of HDAC1 to in vitro-cultured cumulus oocyte complexes (COCs). The results showed that the cumulus cell expansion and oocyte maturation ratio were impaired, while the production of the epidermal growth factor (EGF) was only slightly changed, despite the fact that the pan-acetylation levels of the histones were significantly elevated. This study implies that HDAC1 may participate in the maturation of oocytes in Tan sheep independently of the classic gonadotrophin-induction pathway.Previous studies have shown that some of the histone deacetylases (HDACs) play diverse roles in the regulation of ovarian somatic cell development, oocyte maturation and early embryonic development in different species including sheep. This study aimed to clarify whether HDAC1 also played pivotal roles in regulating oocyte maturation in Tan sheep. The results showed that HDAC1 was expressed in the nuclei of both the granulosa cells and oocytes of the growing follicles in the Tan sheep’s ovaries. However, the level of HDAC1 was unaffected by luteinizing hormone (LH) induction in cultured granulosa cells. Meanwhile, the specific inhibition of HDAC1 using pyroxamide did not induce significant changes in the expression levels of EGF-like growth factors in vitro, whereas both the cumulus expansion and oocyte maturation of the cultured cumulus oocyte complexes (COCs) were significantly inhibited by pyroxamide. Additionally, the numbers of histone acetylation sites (H4K5, H4K12, H3K14 and H3K9) in ovarian granulosa cells were significantly increased. In conclusion, a constant expression of HDAC1 in the growing follicles of Tan sheep may be pivotal for supporting oocyte growth and maturation, although its action may not be closely correlated with LH induction, nor does it directly affect the expression of the EGF-like factors. Our study implies that there may exist diverse functions of the respective HDACs in modulating female reproduction in sheep.

Progesterone Receptors in AVPV Kisspeptin Neurons Are Sufficient for Positive Feedback Induction of the LH Surge.

Kisspeptin, encoded by Kiss1, stimulates gonadotropin-releasing hormone neurons to govern reproduction. In female rodents, estrogen-sensitive kisspeptin neurons in the rostral anteroventral periventricular (AVPV) hypothalamus are thought to mediate estradiol (E2)-induced positive feedback induction of the preovulatory luteinizing hormone (LH) surge. AVPV kisspeptin neurons coexpress estrogen and progesterone receptors (PGRs) and are activated during the LH surge. While E2 effects on kisspeptin neurons have been well studied, progesterone's regulation of kisspeptin neurons is less understood. Using transgenic mice lacking PGR exclusively in kisspeptin cells (termed KissPRKOs), we previously demonstrated that progesterone action specifically in kisspeptin cells is essential for ovulation and normal fertility. Unlike control females, KissPRKO females did not generate proper LH surges, indicating that PGR signaling in kisspeptin cells is required for positive feedback. However, because PGR was knocked out from all kisspeptin neurons in the brain, that study was unable to determine the specific kisspeptin population mediating PGR action on the LH surge. Here, we used targeted Cre-mediated adeno-associated virus (AAV) technology to reintroduce PGR selectively into AVPV kisspeptin neurons of adult KissPRKO females, and tested whether this rescues occurrence of the LH surge. We found that targeted upregulation of PGR in kisspeptin neurons exclusively in the AVPV is sufficient to restore proper E2-induced LH surges in KissPRKO females, suggesting that this specific kisspeptin population is a key target of the necessary progesterone action for the surge. These findings further highlight the critical importance of progesterone signaling, along with E2 signaling, in the positive feedback induction of LH surges and ovulation.

Luteinizing hormone facilitates angiogenesis in ovarian epithelial tumor cells and metformin inhibits the effect through the mTOR signaling pathway

High levels of gonadotropin are a risk factor for ovarian cancer development. Aberrant gonadotropin levels benefit tumor angiogenesis, but the detailed mechanism is not clear. Therefore, the aim of this study was to investigate the molecular mechanism of high levels of luteinizing hormone (LH) on the promotion of tumor angiogenesis and to outline a feasible therapeutic strategy. Western blotting and immunofluorescence staining were used to determine the effect of LH on VEGF and slit2 expression and examine the signaling pathway involved in regulating the expression of both molecules. Real-time PCR was used to investigate the effect of metformin on LH induction of VEGF and slit2 expression. It was found that 50 mIU/ml LH significantly upregulated VEGF and slit2 expression, and activated the PI3K/AKT-mTOR signaling pathway. However, metformin inhibited the mTOR signaling pathway and further blocked LH-induced VEGF and slit2 expression. In conclusion, high levels of LH promote angiogenesis in ovarian cancer via the PI3K/AKT-mTOR pathway. However, metformin could inhibit tumor angiogenesis by blocking the mTOR signaling pathway.

MAPK3/1 (ERK1/2) in Ovarian Granulosa Cells Are Essential for Female Fertility

A surge of luteinizing hormone (LH) from the pituitary gland triggers ovulation, oocyte maturation, and luteinization for successful reproduction in mammals. Because the signaling molecules RAS and ERK1/2 (extracellular signal-regulated kinases 1 and 2) are activated by an LH surge in granulosa cells of preovulatory follicles, we disrupted Erk1/2 in mouse granulosa cells and provide in vivo evidence that these kinases are necessary for LH-induced oocyte resumption of meiosis, ovulation, and luteinization. In addition, biochemical analyses and selected disruption of the Cebpb gene in granulosa cells demonstrate that C/EBPbeta (CCAAT/Enhancer-binding protein-beta) is a critical downstream mediator of ERK1/2 activation. Thus, ERK1/2 and C/EBPbeta constitute an in vivo LH-regulated signaling pathway that controls ovulation- and luteinization-related events.

Luteinizing Hormone-Dependent Activation of the Epidermal Growth Factor Network Is Essential for Ovulation

In the preovulatory ovarian follicle, mammalian oocytes are maintained in prophase meiotic arrest until the luteinizing hormone (LH) surge induces reentry into the first meiotic division. Dramatic changes in the somatic cells surrounding the oocytes and in the follicular wall are also induced by LH and are necessary for ovulation. Here, we provide genetic evidence that LH-dependent transactivation of the epidermal growth factor receptor (EGFR) is indispensable for oocyte reentry into the meiotic cell cycle, for the synthesis of the extracellular matrix surrounding the oocyte that causes cumulus expansion, and for follicle rupture in vivo. Mice deficient in either amphiregulin or epiregulin, two EGFR ligands, display delayed or reduced oocyte maturation and cumulus expansion. In compound-mutant mice in which loss of one EGFR ligand is associated with decreased signaling from a hypomorphic allele of the EGFR, LH no longer signals oocyte meiotic resumption. Moreover, induction of genes involved in cumulus expansion and follicle rupture is compromised in these mice, resulting in impaired ovulation. Thus, these studies demonstrate that LH induction of epidermal growth factor-like growth factors and EGFR transactivation are essential for the regulation of a critical physiological process such as ovulation and provide new strategies for manipulation of fertility.

Ovarian follicle growth, maturation, and ovulation in teleost fish

Knowledge of ovarian follicle growth, maturation, and ovulation in teleosts is important to many aspects of basic and biomedical research, fisheries management, aquaculture, and environmental science. Follicle growth includes previtellogenic and vitellogenic stages. Although little progress has been made in our understanding of previtellogenic development, information on the regulation and mechanisms of vitellogenic growth has increased substantially in recent years. This new information pertains to the multiplicity of vitellogenin (Vg) genes, the oocyte Vg receptor, Vg processing enzymes (cathepsins) and their specific yolk products, and synthesis of various vitelline envelope precursor proteins in liver and ovary. Oocyte acquisition of lipids from sources other than Vg dominates follicle growth in many teleosts, especially perciformes, yet our understanding of the basic processes involved remains rudimentary. Considerable advances also have been made in our understanding of the endocrine regulation and mechanisms of ovarian follicle maturation. We have learned that ovarian follicle maturation involves a number of events including luteinizing hormone (LH)-dependent acquisition of oocyte maturational competence, LH induction of maturation-inducing hormone (MIH) synthesis, and MIH-dependent meiotic resumption (nuclear maturation) and cytoplasmic maturation. While much has been learned about mechanisms of maturational competence, MIH synthesis and meiotic resumption, our knowledge of cytoplasmic maturation is limited to descriptions of MIH-dependent yolk protein hydrolysis and associated oocyte hydration in a few species. It has become apparent that ovulation requires genomic activation regulated by nuclear MIH receptors, but the transduction pathways for the ovulatory MIH signal appear to be complex and are poorly understood.

Luteinizing hormone induction of ovarian tumors: oligogenic differences between mouse strains dictates tumor disposition.

The use of fertility drugs has continued to grow since their introduction in the 1960s. Accompanying this increase has been the speculation that repetitive use of these drugs can cause ovarian tumors or cancer. We recently reported that transgenic mice with chronically elevated luteinizing hormone (LH), an analog of which is commonly used in fertility regimens, develop granulosa cell (GC) tumors. In this report we show that LH induction of these tumors is highly dependent on genetic background. In CF-1 mice, chronically elevated LH invariably causes GC tumors by 5 months of age. However, in hybrid mice generated by crossing CF-1 males with C57BL/6, SJL, or CD-1 females, elevated levels of this same hormone cause a completely different phenotype resembling a luteoma of pregnancy. We also show that three genes likely control these alternative hormonal responses. This clinical correlate of elevated LH reveals remarkably distinct, strain-dependent, ovarian phenotypes. In addition, these results support the rare incidence of GC tumors in the human population, and suggest that the ability of certain fertility drugs to cause ovarian tumors may depend on an individual's genetic predisposition.

Expression of Functional Luteinizing Hormone (LH) Receptor and Its Messenger Ribonucleic Acid in Bovine Uterine Veins: LH Induction of Cyclooxygenase and Augmentation of Prostaglandin Production in Bovine Uterine Veins

Expression of Functional Luteinizing Hormone (LH) Receptor and Its Messenger Ribonucleic Acid in Bovine Uterine Veins: LH Induction of Cyclooxygenase and Augmentation of Prostaglandin Production in Bovine Uterine Veins

Expression of functional luteinizing hormone (LH) receptor and its messenger ribonucleic acid in bovine uterine veins: LH induction of cyclooxygenase and augmentation of prostaglandin production in bovine uterine veins.

We have previously reported that bovine endometrium contains LH/human CG binding receptors and LH induces cyclooxygenase and prostaglandin production in the bovine endometrium. The present study investigated 1) whether bovine uterine vein and artery contain LH receptor messenger RNA (mRNA) and receptor protein and 2) whether LH can regulate the formation of vasoactive eicosanoids by the uterine vein. The uterine vein endothelium, but not the uterine artery, contained LH receptor mRNA transcript essentially identical to that found in the bovine corpus luteum. The uterine vein endothelium also contained a 95-kDa immunoreactive receptor protein that bound to rat anti-LH receptor antibody in Western blots. The LH receptor mRNA and LH receptor were maximally expressed in the uterine vein from cows in proestrus/estrus compared with cows in luteal or postovulatory phases. Incubation of endothelial minces of uterine vein with LH resulted in a 2-fold increase in cyclooxygenase concentration as determined by Western blot using an antibody to ram seminal vesicle cyclooxygenase. The increase in cyclooxygenase was maximal in cows in proestrus/estrus compared with postovulatory and luteal phase cows. Incubation of proestrous/estrous uterine vein or artery minces with LH or mellitin (a phospholipase A2 stimulator) caused increased production of eicosanoids. In the uterine vein, LH caused a significant increase in both PGF2alpha (basal 4.1 +/- 0.4 vs. 5.7 +/- 0.4 ng/100 mg x 6 h, P < 0.01; N = 9 cows) and PGE2 (basal 5.7 +/- 0.3 vs. 7.7 +/- 0.8 ng/100 mg x 6 h, P < 0.01; N = 6 cows) but had no effect on prostaglandin production by the artery. Mellitin increased PGF2alpha production by both uterine vein and artery minces but had no effect on PGE2 production in either tissue. Addition of steroids (progesterone, estradiol) or cytokines (tumor necrosis factor-alpha, IL-6) to the uterine vascular tissues had essentially no effect on prostanoid production. In summary, bovine uterine vein from proestrous/estrous cows expressed the LH receptor and its mRNA. Expression of the receptor may have physiological significance as LH induces cyclooxygenase and increases prostaglandin release in the uterine vein. The maximal stimulation of the receptor and its mRNA at proestrus/ estrus may serve to increase the amounts of prostanoids reaching the regressing corpus luteum either directly by increasing prostanoid production or indirectly by increasing the blood flow to the ovary.

Luteinizing hormone induction of the cholesterol side-chain cleavage enzyme in cultured immature rat Leydig cells: No role of insulin-like growth factor-I?

Long-term inductive effects of luteinizing hormone (LH) on cholesterol side-chain cleavage (CSCC) enzyme activity were studied, using cultured Leydig cells isolated from 21-day-old rats. Particular reference was given to the role of insulin-like growth factor-I (IGF-I) as an autocrine or paracrine modulator or as an essential extracellular mediator of LH action. The CSCC enzyme activity was measured using an excess of 22( R-hydroxycholesterol as substrate to saturate the enzyme, and inhibitors of pregnenolone metabolism to concentrate all the products of the enzyme reaction in pregnenolone. The rate of sterol conversion into pregnenolone (CSCC enzyme activity) reflected the amount of cytochrome P-450 scc ( P-450 scc), as was shown by Western blotting. In cells cultured without LH, the CSCC enzyme activity decreased to 10% on day 7 of the culture period. In the presence of various doses of LH ranging from 0.01 to 100 ng/ml, the CSCC enzyme activity also diminished during the first 3 days of culture, but during the following days, the amount of CSCC enzyme was stimulated by LH. In contrast to the absence of any LH effect on the activity of the CSCC enzyme during the first days of the culture, the endogenous steroid production (no added 22( R)-hydroxycholesterol) could be stimulated at least 10-fold by high doses of LH. When LH (1 ng/ml) was added to cells which had been cultured for 7 days without hormones, CSCC enzyme activity was elevated 8-fold after 4 days of exposure of LH. These effects of LH could be mimicked by dbcAMP (0.5 mM). No evidence could be provided that IGF-I plays any role in the LH induction of the CSCC enzyme; neither the addition of exogenous IGF-I or analogs that do not bind to IGF-I binding proteins (IGFBPs) nor the inactivation of endogenous IGF-I action (through binding to IGFBP and antibodies to IGF-I or via masking of IGF-I receptor by antibodies) could influence the LH induced CSCC enzyme activity. The present data raise the question under which conditions IGF-I is capable of modulating Leydig cell Steroidogenesis.

Stimulation of endogenous surge of luteinizing hormone with gonadotropin-releasing hormone analog after ovarian stimulation for in vitro fertilization

The effect of induction of preovulatory endogenous surge of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) with intranasal administration of GnRH-analog (GnRH-a) in an in vitro fertilization (IVF) program is reported. The use of GnRH-a resulted in a significantly better percentage of replaceable embryos (91% versus 85%). The pregnancy rate was 51% in comparison with 32% in control cycles in which follicular maturation was achieved by human chorionic gonadotropin administration. There was no significant difference in the postoocyte recovery serum progesterone patterns between the two groups. Our results indicate that the induction of endogenous LH and FSH surge with GnRH-a may be successfully employed for final follicular maturation after ovarian suprastimulation without affecting the outcome of IVF adversely. Apart from being a more physiological approach to oocyte maturation, it also has potential economic and clinical advantages.

Luteinizing Hormone (LH)-Releasing Hormone: Effects on Induction of LH, Follicle-Stimulating Hormone, and Prolactin Cell Differentiation*

We investigated the influence of LHRH on the differentiation of gonadotrophs and lactotrophs in fetal pituitary glands transplanted beneath the renal capsules of adult hypophysectomized-orchidectomized hamsters (hosts). Hypophyses were removed from hamster fetuses at a gestational age of 14 days. Some of these were immediately fixed in Bouin's solution, and others were transplanted into the hosts. The hosts were injected sc twice daily with 1 microgram LHRH or vehicle for 16 days. Six hosts in each group were killed by decapitation 16 h after the last injection. Six 14-day-old normal male hamsters (age-matched to correspond to the age of the allografts at the time of the hosts' decapitation) also were decapitated. Sections of hypophyses in situ from fetal hamsters, from 14-day-old controls, and from allografts in each group were stained for LH, FSH, or PRL and with hematoxylin. No PRL-containing cells and very few LH or FSH cells (less than 0.025% of the adenohypophysial cell population) were observed in fetal pituitary glands. In allografts from the vehicle-treated hosts, 21.1% of adenohypophysial cells contained LH, but only 1.8% contained FSH. In allografts from LHRH-treated hosts, 28.0% and 22.9% of the adenohypophysial cells contained LH and FSH, respectively. Adenohypophyses that developed for the same length of time in situ had smaller percentages of adenohypophysial cells containing LH (23.8%) and FSH (15.5%) than the LHRH-treated group. LH-containing cells in allografts in the vehicle-treated hamsters, but not in the LHRH-treated animals, were reduced in size compared to those measured in situ. The number of lactotrophs in all allografted tissue was markedly reduced compared to that of lactotrophs in situ, and injection of LHRH into hamsters with allografts did not alter the percentage of adenohypophysial cells that were lactotrophs. These results suggest that in the hamster LHRH 1) plays an important role in stimulating the formation of immunoreactive FSH in the pituitary gland, 2) can increase the number of gonadotrophs that develop during the neonatal period, and 3) plays a role in controlling the size of gonadotrophs during development. The results also suggest that the development of lactotroph cell number requires close proximity to the hypothalamus and/or exposure to a neonatal environment. We found no evidence to support the view that LHRH, LH, or FSH stimulates immunoreactive lactotroph differentiation.

Is serotonin involved in the ovulatory process of the rat ovary perfused in vitro?

The presence of 5-HT (serotonin) in ovarian tissue and its varying concentrations during the oestrous cycle suggests that it takes part in ovarian function and in the ovulatory process as one of several mediators of the inflammatory-type reaction preceding follicular rupture. With the aid of a recirculating perfusion model, in which the central stimulatory action of 5-HT was avoided, its direct ovarian effect on ovulation was studied using immature, pregnant, mare serum gonadotrophin (PMSG)-treated rats. Four out of five ovaries ovulated after the addition of 5-HT to the perfusion medium, though the ovulation rate (0.8 per ovary) did not reach the order of magnitude seen after luteinizing hormone (LH) stimulation (5.4 per ovary). The selective 5-HT2 receptor antagonist, ketanserin, did not significantly reduce the 5-HT induced ovulations, and moreover, reduced the LH-stimulated ovulations. The calcium entry blocker, nifedipine, had no effect on either 5-HT or LH induction ovulations.

Temporal relationship of the prolactin‐dependent LH‐induced LH receptor to the LH stimulus

The time course for LH induction of luteinizing hormone (LH) receptors as reflected in binding of 125I-labeled hCG was investigated in hypophysectomized adult male rats. A low dose of oLH (10 micrograms) was administered to hypophysectomized adult male rats following pretreatments with prolactin, follicle-stimulating hormone (FSH), growth hormone (GH), or saline. Testicular binding of hCG was determined at different times following the LH injection using Leydig cell membrane preparations from a testicular homogenate. Seven days after hypophysectomy, hCG binding was at a nadir of 19 +/- 7% (mean +/- SD) of control values. Pretreatment with prolactin (100 micrograms/day) for 7 days was associated with a nonsignificantly different hCG binding that was 30 +/- 5% of control values. Prolactin pretreatment plus a single 10 micrograms LH i.p. injection increased 125I hCG binding up to 56 +/- 10% of control values within 30 minutes of the LH injection. Luteinizing hormone-induced hCG binding persisted at a high level (51 +/- 4% of control values) for 2 hours but returned to hypophysectomized control levels 6 hours after the i.p. LH injection. Seven days pretreatment with FSH or GH at 100 micrograms/day plus 10-micrograms LH injections was also tested. Neither FSH nor GH had a statistically significant effect on hCG binding nor could they mimic the ability of prolactin to allow for LH induction of hCG binding in the hypophysectomized adult male rats. These studies suggest that the induction or "up-regulation" of Leydig cell hCG binding by ovine LH is rapid and specifically dependent upon pre-exposure to prolactin.

Characteristics of prolactin-modulated LH induction of LH/hCG receptors. Transient inhibition of receptor induction following prolactin exposure.

The temporal relationship between exposure to prolactin (PRL) and luteinizing hormone (LH) induction of LH receptors was investigated in hypophysectomized adult male rats. Testicular homogenate membrane preparations were incubated with [125I]hCG for analysis of LH/hCG binding. Seven days after hypophysectomy, the rats were injected with 100 micrograms/day of PRL for another 7 days and then given a single 10-micrograms dose of LH at 2, 4, 6, 12, 24, or 36 hours after the last PRL injection. The priming effect of PRL on LH induction of receptors was not observed if LH was administered 2 to 12 hours from the last PRL injection. However, after this inhibitory period, injections of LH to PRL-primed rats resulted in induction of LH receptors and the effect persisted for 36 hours. This study supports previous reports demonstrating a unique dependence upon PRL for LH up-regulation of the LH receptor and characterizes the brief refractory period following exposure to PRL.

Anisomycin inhibition of estradiol-induced and progesterone-facilitated luteinizing hormone surges in the immature rat.

These studies were designed to examine the effect of anisomycin, a potent and reversible inhibitor of protein synthesis with low systemic toxicity in rodents, on induction of luteinizing hormone (LH) surges by estradiol and their facilitation by progesterone. Immature female rats that received estradiol implants at 0900 h on Day 28 had LH surges approximately 32 h later (1700 h on Day 29). Insertion of progesterone capsules 24 h after estradiol led to premature (by 1400 h) and enhanced LH secretion. Protein synthesis was inhibited by 97%, 95%, 47%, and 16% in the hypothalamus-preoptic area (HPOA) and by 98%, 87%, 35%, and 0% in the pituitary at 30 min, 2 h, 4 h, and 6 h after s.c. injection of anisomycin (10 mg/kg BW), respectively. A single injection of anisomycin at 0, 3, 6, 9, 12, 24, 27, or 30 h after estradiol treatment significantly lowered serum LH levels at 32 h. The effect of injecting anisomycin at 0, 24, or 27 h was overridden by progesterone treatment at 24 h, but LH secretion was delayed serum LH levels were basal (10-30 ng/ml) at 1400 h but elevated (500-800 ng/ml) at 1700 h. Complete suppression of LH surges in estradiol-plus-progesterone-treated rats was achieved with 2 injections of anisomycin on Day 29 at 0900 h and again at 1200 h or 1400 h. Further experiments were designed to examine proteins that might be involved in anisomycin blockade of progesterone-facilitated LH surges. Intrapituitary LH concentrations at 1700 h on Day 29 were 70-80% higher (102 +/- 12.5 micrograms/pituitary) in rats that received 2 injections of anisomycin than in vehicle-treated controls (58.5 +/- 7.7 micrograms/pituitary). There were no significant effects of anisomycin on cytosol progestin receptors in the HPOA (7.1 +/- 1.5 fmol/tissue, anisomycin; 7.2 +/- 0.3, vehicle) or pituitary (8.3 +/- 1.3 fmol/tissue, anisomycin; 11.7 +/- 2.9, vehicle) at this time. The concentration of pituitary gonadotropin-releasing hormone receptors (GnRH-R), however, was significantly lower after anisomycin (265 +/- 30 vs. 365 +/- 37 fmol/mg protein) treatment. These results suggest that both estradiol-induced and progesterone-facilitated LH surges involve protein synthetic steps extending over many hours. Blockade of progesterone-facilitated LH surges by anisomycin appears to be due primarily to an effect on release of LH to which lowering of GnRH-R levels may contribute.

Synergistic interactions of somatomedin-C with adenosine 3',5'-cyclic monophosphate-dependent granulosa cell agonists.

Recent studies have demonstrated the ability of somatomedin-C (Sm-C) to synergize with follicle-stimulating hormone (FSH) in the activation of cultured rat granulosa cell progesterone biosynthesis as well as the induction of luteinizing hormone (LH) receptors. Neither effect could be attributed to Sm-C-enhanced granulosa cell survival or replication, but could be accounted for, in part, by increased adenosine 3',5'-cyclic monophosphate (cAMP) generation. The present study was undertaken to determine if the synergistic property of Sm-C is FSH-selective and hence limited in relevance to follicular maturation, as well as to clarify further the role of cAMP in Sm-C-amplified agonist action. To this end, the ability of Sm-C to modulate the hormonal action of a series of physiologic as well as pharmacologic granulosa cell agonists was examined in vitro using cultured granulosa cells from immature, hypophysectomized, diethylstilbestrol-treated rats. Concurrent treatment with highly purified Sm-C (50 ng/ml) resulted in marked increases over controls in the LH-stimulated [1 ng human chorionic gonadotropin (hCG)]-and beta 2-adrenergic-stimulated (10(-6) M terbutaline) accumulation of cAMP (3.8- and 2.6-fold, respectively and progesterone (3.2- and 7.4-fold, respectively). Similarly, concurrent treatment with Sm-C also augmented the vasoactive intestinal peptidergic stimulation of granulosa cell cAMP generation (4.1-fold) and progesterone biosynthesis (2.1-fold). In contrast, Sm-C was incapable of enhancing progesterone accumulation in response to stimulation with rat prolactin, a cAMP-independent granulosa cell agonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of serum-free defined medium in regulation of LH receptor in cultured rat granulosa cells

The induction of luteinizing hormone (LH) receptor by follicle-stimulating hormone (FSH) in granulosa cells was compared following culture in serum-free or serum-containing medium. Incubation of primary cultures of granulosa cells in serum-free defined medium with purified FSH resulted in dramatic increases in the level of functional LH receptors. This striking enhancement of LH receptor by FSH was completely abolished by concomitant incubation with serum (rat, horse, porcine, human or calf). The serum inhibition of FSH was not readily reversible and could be evoked throughout the culture period. The synthesis of cAMP by FSH was markedly suppressed by serum, suggesting that serum component(s) are inhibiting FSH action at the level of adenylate cyclase. Such an action, however, cannot be the sole mechanism because serum also blocked LH receptor induction by cyclic AMP analogs. In defined medium, addition of insulin, transferrin, dexamethasone or fibronectin alone had no effect on basal levels of LH receptor. However, following incubation with either insulin or dexamethasone, the FSH-induced increases in LH receptor were markedly suppressed. Insulin was found to markedly inhibit FSH-stimulated cyclic AMP formation; this was not the case with dexamethasone. The present results demonstrated the complete inhibition of FSH action by serum in cultured granulosa cells and suggest that the effect is caused by a combination of direct actions of common metabolic hormones which inhibit FSH action at multiple sites. These experiments clearly indicate the obligatory role of defined medium in the hormone-dependent differentiation of the granulosa cell in culture.

Epidermal growth factor and gonadotropin‐releasing hormone inhibit cyclic AMP–dependent luteinizing hormone receptor formation in ovarian granulosa cells

The induction of luteinizing hormone (LH) receptors was studied in granulosa cells prepared from the ovaries of hypophysectomized diethylstilbestrol-treated immature rats. Incubation of granulosa cells for 48 h with increasing concentrations of follicle-stimulating hormone (FSH) or choleragen caused parallel rises in cAMP levels and LH receptors. These observations, with the finding that 8-Bromo-cAMP also induced LH receptor formation, indicate that hormonal stimulation of LH binding sites is mediated by cAMP. Peptide hormones that inhibited FSH-stimulated cAMP production, such as epidermal growth factor (EGF) and a gonadotropin-releasing hormone agonist (GnRHa), also prevented LH receptor formation. GnRHa and EGF had negligible effects on FSH-stimulated cAMP production from 0 to 24 h of culture, but reduced cAMP accumulation by 80% and 90%, respectively, from 24 to 48 h when the majority of LH receptors appeared. FSH-sensitive adenylate cyclase activity, as measured by the conversion of (3H)-ATP to (3H)-cAMP, was inhibited by GnRHa and EGF at 48 h of culture. EGF and GnRHa also reversed the inhibiton of ectophosphodiesterase activity caused by FSH in granulosa cells between 48 and 72 h of culture. Both EGF and GnRHa inhibited induction of LH receptors by 8-Bromo-cAMP, suggesting that their effects are also on cAMP action. Addition of GnRHa, but not EGF, between 36 and 48 h of culture completely prevented further increases in LH receptors induced by 8-Bromo-cAMP, indicating that the inhibitory action of GnRHa can be initiated at later times during granulosa cell differentiation, whereas full expression of EGF action requires a longer period. These results demonstrate that EGF and GnRH inhibit FSH-induced LH receptor formation in the granulosa cell by reducing hormone-dependent cAMP production and also by impairing the ability of cAMP to stimulate LH receptor formation.

Behavioral and neuroendocrine effects of long-term progesterone treatment in the rat.

Progesterone and estradiol, alone or in combination, were administered to ovariectomized rats for 2 weeks. Progesterone alone had no effect on body weight, luteinizing hormone (LH) secretion, receptivity or brain cytoplasmic progestin receptors (CPR). Progesterone in combination with estradiol significantly attenuated estrogen suppression of weight gain and estrogen stimulation of receptivity, the LH afternoon surge and induction of CPR, but did not affect the negative feedback of estrogen on morning LH levels. The decrease in CPR after 2 weeks of progesterone is very similar in magnitude to the decrease observed following acute treatment, suggesting that, unlike neurotransmitter agonists and glucocorticoids, progesterone does not cause down regulation of its receptors in the brain following chronic treatment.