Comparison of growth hormone and insulin-like growth factor-I regulation of estradiol and progesterone production in human luteinized granulosa cells

Growth hormone (GH) appears to affect the timing of puberty in children. The effects of GH on puberty may be related to direct GH action on ovarian function or may be mediated by IGF-I. To determine the likelihood that GH has direct effects on ovarian function, we compared the ability of GH and IGF-I to increase luteinized granulosa cell steroidogenesis in the absence and presence of gonadotropins. Cells were obtained from women undergoing in vitro fertilization for tubal disorders or male factor infertility and were placed in static culture. GH alone failed to alter progesterone or estradiol accumulation in the medium of cultured luteinized granulosa cells. IGF-I produced no increase in progesterone accumulation but increased estradiol accumulation 5.6-fold compared with cells treated with vehicle. The combination of GH and FSH produced an 0.83-fold increase in estradiol accumulation, whereas the combination of IGF-I and FSH resulted in a 2.9-fold increase in estradiol accumulation above FSH alone. Thus the direct effects of GH on granulosa cell steroid synthesis are modest compared with those of IGF-I. If GH has an effect on ovarian development at puberty, it is likely to be mediated by a GH-induced increase in circulating IGF-I.

Evidence for follicle-stimulating hormone mediation in the hemiorchidectomy-induced compensatory increase in the function of the remaining testis of the adult male bonnet monkey (Macaca radiata)

Hemiorchidectomy (HO) in the adult male bonnet monkey results in a selective increase in circulating concentrations of FSH and testosterone, and this is accompanied by compensatory increase in sperm production by the remaining testis. We investigated the possible role of increased FSH concentration that occurs after HO in the compensatory increase in the activity of the remaining testis. Of eight adult male bonnet monkeys that underwent HO, four received i.v. injections every other day for 30 days of a well-characterized ovine FSH antiserum (a/s) that cross-reacts with monkey FSH. The remaining four males received normal monkey serum (NMS) as control treatment in a protocol similar to that employed for a/s-treated males. Blood samples were collected between 2100 and 2200 h before and 1/2, 1, 3, 5, 7, 14, 22, and 29 days after HO. Testicular weight, number of 3 beta-hydroxy steroid dehydrogenase-positive (3 beta-HSD+) cells, and DNA flow cytometric analysis of germ cell populations were obtained for testes collected before and at the termination of NMS or a/s treatment. In NMS-treated males, circulating serum FSH concentrations progressively increased to reach a maximal level by Day 7 after HO (1.95 +/- 0.3 vs. 5.6 +/- 0.7 ng/ml on Days -1 and 7, respectively). Within 30 min of a/s injection, FSH antibodies were detected in circulation, and the antibody level was maintained at a constant level between Day 7 and end of treatment (exhibiting 50-60% binding to 125I-hFSH).(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneity of follicle stimulating hormone: control and physiological function

The existence of a heterogeneous population of follicle stimulating hormone (FSH) was described many years ago. Other pituitary glycoproteins, such as thyroid stimulating hormone (TSH) and luteinizing hormone (LH) as well as placental human chorionic gonadotrophin (HCG) also exhibit heterogeneity. Because FSH plays a significant role in a variety of ovarian activities such as follicular maturation, selection of the dominant follicle and ovulation, the possible role of subpopulations of FSH with distinct physicochemical characteristics is of great interest. After a great deal of investigation, the physiological significance of this biochemical phenomenon has yet to be fully understood. Investigators have employed immunoassays, in-vitro bioassays and radioreceptor assays to study the biological activity of the individual isoforms of FSH. As more information has accumulated, it has become clear that some of the initial assumptions used to interpret data may be incorrect. This review is provided to update the reader with available information on the topic as it relates to FSH and to point out issues that require re-evaluation in this area.

The effects of recombinant follicle-stimulating hormone on the restoration of spermatogenesis in the gonadotropin-releasing hormone-immunized adult rat

The role of FSH in spermatogenesis is unclear as testosterone alone has been reported to be sufficient in the gonadotropin-deficient rat. This study examined the effects of recombinant FSH on the restoration of spermatogenesis after gonadotropin withdrawal by GnRH immunization. Adult Sprague-Dawley rats received GnRH immunogen (100 micrograms, sc, every 4 weeks) to induce gonadotropin deficiency, with severe spermatogenic regression occurring by 12 weeks. Recombinant human FSH was then given (10 or 50 IU/kg, sc, daily) for 7, 14, and 21 days, with data from both dosages combined in the analyses. Testes were perfusion fixed, and germ cell numbers were quantified by the optical disector technique. After 7 days of FSH, testis weight significantly increased by 43% (P < 0.01), with no further increases at 14 and 21 days. GnRH immunization severely reduced germ cell numbers, which were then significantly (P < 0.05) restored in all cell types, except elongated spermatids, by 7 days of FSH; type A spermatogonia (45%-->61% of control), type B spermatogonia/preleptotene spermatocytes (46%-->65%), leptotene/zygotene spermatocytes (39%-->55%), pachytene spermatocytes in stages I-VIII (11%-->30% control) and IX-XIV (4.3%-->22% control), and round spermatids in stages I-VIII (1.4%-->4.4% control). Prolonged FSH treatment did not further increase type A spermatogonial or pachytene spermatocyte number, whereas round spermatids increased to a peak of 12.8% of the control value. At no stage did FSH increase elongated spermatid numbers above 1% of the control level. The incorporation of bromode-oxyuridine into spermatogonial and early spermatocyte nuclei did not change after GnRH immunization or FSH treatment. Sertoli cell number was not altered by any treatment; however, Sertoli cell nuclear volume was significantly decreased from the control value by GnRH immunization (142 +/- 9 vs. 455 +/- 22 microns 3; P < 0.01) and increased after 7 and 14 days of FSH treatment to 212 +/- 10 and 259 +/- 24 microns 3, respectively. FSH treatment restored serum inhibin levels to normal, but did not increase serum or testicular androgen levels. We conclude that recombinant FSH partially restores spermatogenesis in the gonadotropin-deficient rat by increasing the number of spermatogonia and promoting subsequent maturational steps up to the round spermatid stage. Spermatid elongation was not restored by FSH, indicating the need for an additional factor(s), most likely testosterone.

Follicle stimulating hormone-granulosa cell axis involvement in the antifolliculotrophic effect of low dose mifepristone (RU486)

This study was designed to assess the involvement of follicle stimulating hormone (FSH)-granulosa and luteinizing hormone (LH)-theca axes in the antifolliculotrophic effect of mifepristone. Plasma gonadotrophins, including plasma LH bioactivity and pulsatility, oestradiol, testosterone and inhibin concentrations, and follicular growth were monitored in volunteer women treated with placebo or mifepristone in two consecutive cycles. Mifepristone was given either as a single dose of 5 mg (n = 7) when the leading follicle had reached a diameter between 12 and 14 mm, or as a multiple dose of 5 mg/day for 3 days, beginning when the leading follicle had reached a diameter between 14 and 16 mm (n = 5) or between 6 and 11 mm (n = 5). Following the single dose of mifepristone, follicular growth and the accompanying increase in plasma oestradiol were arrested at 12 and 36 h respectively without changes in gonadotrophin or testosterone serum concentrations. The 3 day regimen arrested follicular growth and oestradiol rise and decreased plasma inhibin concentrations when follicles were larger than 12 mm at the onset of treatment. These results indicate that the antifolliculotrophic action of mifepristone is associated with a selective compromise of the FSH-granulosa axis of dominant follicles that have passed a critical stage of growth.

Inositol lipid-mediated signalling in response to endothelin and ATP in the mammalian testis

The testis is a complex organ in which local control is achieved by signalling between its constituent cells. Herein we describe the responses of cultured rat testicular cells and a mouse Sertoli cell-line to stimulation by endothelin and ATP, and elsewhere we have shown that rat peritubular myoid cells possess phosphoinositidase C-coupled V1a-vasopressin receptors identical to those of liver (Howl, J. et al, 1995, Endocrinology 136: 2206-2213). 1. Peritubular myoid cells from pre-pubertal rats responded through ETA receptors with PtdIns(4,5)P2 hydrolysis [EC50 for endothelin-1 (ET-1) approximately 0.4 nM], elevation of intracellular [Ca2+], and tyrosine phosphorylation of a variety of cellular proteins. They also showed enhanced adenylate cyclase activity, with an EC50 for ET-1 of approximately 3 nM, also through ETA receptors. Pharmacological elevation of [cAMP] did not immediately change the ET-1-stimulated formation of inositol phosphates, but attenuated the response after several hours. 2. Pre-pubertal rat Sertoli cells showed no detectable responses to ET-1, but responded to FSH with elevated [cAMP] and to ATP with PtdIns(4,5)P2 hydrolysis. PtdIns(4,5)P2 hydrolysis was equally responsive to ATP and UTP, and so appears to be activated by P2U-purinergic receptors. This response was enhanced by protein kinase C inhibition and attenuated by PKC activation. 3. Despite its lack of effect on rat Sertoli cells in primary culture, ET-1 provoked PtdIns(4,5)P2 hydrolysis in the TM4 murine Sertoli cell line (EC50 approximately 0.6 nM), and this response was negatively regulated by protein kinase C activation. 5. No receptor-stimulated activation of phosphoinositase C was detected in 'germ cell' populations, but the non-specific G protein activator A1F4-provoked inositol phosphate accumulation in these cells, so demonstrating their potential to respond through yet to be identified G protein-coupled receptors with phosphoinositidase C activation. 6. Immunoblotting studies showed the presence in rat testis of phosphoinositidase C-beta 1 and the alpha-subunits(s) of the G-protein(s) Gq and/or G11. These studies show that testicular myoid and Sertoli cells use at least three G protein-coupled receptors (V1a-vasopressins, ETA-endothelin and P2U-purinergic) to signal through phosphoinositidase C activation, that ET-1 can activate multiple signalling pathways in myoid cells, and that the ET-1-stimulated phosphoinositidase C responses of myoid and Sertoli cells have different regulatory characteristics.

GnRH analog administration in patients with polycystic ovarian disease

OBJECTIVE

To evaluate the hormonal response to the short protocol of gonadotropin-releasing hormone (GnRH) analog (GnRHa) in patients with polycystic ovarian disease (PCOD).

METHODS

We enrolled 35 patients (20 infertile) with ultrasonographic and hormonal PCOD characteristics. GnRHa Suprefact was applied subcutaneously at a daily dose of 0.9 ml for 9 consecutive days starting on the 10th-15th day after induced or spontaneous bleeding. Blood sampling for follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T), estradiol (E2), estrone (E1) and dehydroepiandrosterone sulfate (DHEA-S) was performed before the treatment and on days 3 and 4 of GnRHa administration. Student's t-test was used for the analysis of differences between various mean values. All statistical analyses were performed by the computerized statistical package CSS-Statistica.

RESULTS

Pretreatment hormonal levels (FSH 5.68 +/- 1.86 IU/l, LH 14.16 +/- 1.72 IU/l, E2 0.29 +/- 0.20 nmol/l, E1 0.35 +/- 0.17 nmol/l, T 3.52 +/- 1.40 nmol/l, DHEA-S 7.15 +/- 2.89 mumol/l) barely differed on day 3 of GnRHa administration, except for the rise in LH (17.14 +/- 10.97 IU/l), which was still not significant. On day 9 of GnRHa application, significant suppression of FSH (3.16 +/- 1.55 IU/l) and LH (8.05 +/- 5.00 IU/l) was registered compared with pretreatment levels, without changes in the FSH:LH ratio, and in other parameters studied. Although there were no changes in ultrasound characteristics on day 9 of GnRHa administration compared with basal findings, bleeding occurred 14-18 days after the last GnRHa dose in 32 patients. There were three pregnancies out of 20 infertile patients in the treated cycles.

CONCLUSION

Significant suppression of FSH and LH in PCOD patients does not interfere with ovarian steroid production, which is probably maintained due to higher follicular sensitivity to normal FSH and LH levels. Alternatively it may be the consequence of the unaltered FSH:LH ratio in spite of GnRHa-suppressed absolute values. However the recommencement of menstrual bleeding and 15% of pregnancies in the investigated infertile patients suggest the occurrence of certain temporary intraovarian events, which probably continue after the cessation of GnRHa administration.

Expression of the gene encoding transcription factor cyclic adenosine 3',5'-monophosphate (cAMP) response element-binding protein (CREB): regulation by follicle-stimulating hormone-induced cAMP signaling in primary rat Sertoli cells

The somatic Sertoli cells of the testis are major targets for FSH and are important for the regulation of spermatogenesis. The binding of FSH to Sertoli cells activates the cAMP-dependent protein kinase A signaling pathway, resulting in phosphorylation of the cAMP response element-binding protein (CREB), which is required to transactivate genes containing cAMP response elements (CREs). Here we show that the addition of forskolin to cultured primary Sertoli cells results in the phosphorylation of CREB within 2-5 min. Phospho-CREB levels remain elevated with continued forskolin stimulation, but fall by 60% within 5 min after the removal of forskolin. In addition, we found that 8-bromo-cAMP induces CREB RNA accumulation in the Sertoli cells. Transient transfections of primary Sertoli cells with CREB promoter-chloramphenicol acetyltransferase reporter plasmids define a conserved 300-base pair region of the CREB promoter surrounding the transcription start site that is required for both basal and cAMP-inducible expression of the CREB gene. This region of the promoter contains three Sp1-binding sites flanking the transcription initiation site and two CREs located 65 and 85 base pairs downstream of the transcription initiation site. We show that the Sp1 motifs bind Sp1 in Sertoli extracts and contribute to basal promoter activity, and that the CREs bind CREB and are essential for cAMP induction of CREB gene transcription. These findings support the model of FSH- and cAMP-mediated CREB autoregulation of its own promoter and may explain the dramatic stage-specific oscillations in Sertoli cells of CREB messenger RNA levels during the 12-day cycles of spermatogenesis in rat seminiferous tubules.

The 1994 Stevenson Award Lecture. Follicle-stimulating hormone and luteinizing hormone: a tale of two gonadotropins

Although most gonadotropes synthesize both luteinizing hormone and follicle-stimulating hormone, the transcription, content, and secretion rates of the two gonadotropins can be separated. The signals external to the gonadotropic cells that appear to be important in the differential regulation are gonadotropin-releasing hormone pulse frequency (high pulse frequency favors luteinizing hormone), steroid feedback (works on both but induces a more powerful negative feedback on luteinizing hormone), and gonadal peptide feedback (activin increases follicle-stimulating hormone; inhibin and follistatin decrease it). We know very little about the pathways within the gonadotropes that favor one gonadotropin rather than another. It is expected that the cloning of the genes for both gonadotropins and the use of specific cell lines and transfections will lead to elucidation of these pathways.

Pituitary-ovarian interactions during follicular maturation and ovulation

During the past decade, research on hypothalamic-pituitary-ovarian relationships in ovulation has explored the contributions of ovarian steroids and other possible ovarian-derived endocrine factors, such as inhibin, follistatin, and activin. Follistatin and activin probably have a significant intraovarian and intrapituitary function but are not likely to have critical endocrine roles during the follicular phase. Studies carried out with both recombinant and highly purified forms of follicle-stimulating hormone in humans and monkeys indicate that this hormone is the primary stimulant of follicular growth and development. Studies on animals may have led to incorrect emphasis on the local role of estradiol in primate follicular growth. It appears that estradiol is not a critical folliculotropin in humans, although it may have some important direct effects on the oocyte.

Ovarian control of follicle development

A variety of ovarian autocrine and paracrine factors may modulate folliculogenesis and steroid production. The developmental program that leads to the production of a dominant follicle involves a precise quantitative and temporal pattern of expression of a large number of genes. Follicle-stimulating hormone plays an essential role in this process, and no other ligand by itself can serve in this regulatory capacity. It is clear that a variety of growth factors can modulate follicle-stimulating hormone action by autocrine and paracrine mechanisms. Advances in the understanding of the role of growth factors, particularly the family of insulin-like growth factor-related proteins, in regulating follicle-stimulating hormone action are discussed. It is likely that complex interactions exist between follicle-stimulating hormone and the growth factors. Significantly, growth factor regulation by pituitary gonadotropins is probably a central feature of their expression. With increased understanding of the ovarian control of follicle development, it is hoped that newer and more effective regimens for synchronous follicular and oocyte maturation can be realized.

Effects of luteinizing hormone and follicle-stimulating hormone on the progesterone receptor induction in chicken granulosa cells in vivo

Progesterone receptor (PR) is increased in the granulosa cells prior to ovulation. In order to investigate the factors that induce PR in granulosa cells, we examined whether the PR is induced in granulosa cells by the injection of chickens with ovine luteinizing hormone (oLH) or porcine follicle-stimulating hormone (pFSH) by Western blot analysis. In the oLH-stimulated birds, PR of 79 kDa and 110 kDa were recognized in the granulosa cells of the largest follicle, whereas a PR of 110 kDa was observed in those of the smaller follicles (the second and third largest follicles). No immunoreaction product was observed in the granulosa cells of both the largest and the smaller follicles in pFSH-stimulated birds. In the control birds that were injected with saline, no immunoprecipitate was recognized in the granulosa cells of the largest or smaller follicles. These results suggest that LH may be involved in the induction of PR in the granulosa cells prior to ovulation.

Molecular aspects of the ontogeny of the pituitary-gonadal axis

The endocrine function of the mammalian pituitary-gonadal axis begins in utero. This is important particularly for the ontogeny and function of the male reproductive organs, the induction of which is critically dependent on the two fetal testicular hormones, testosterone and anti-müllerian hormone. In contrast, ovarian endocrine activity begins only after birth. The earliest phases of testicular hormone production are probably under autocrine or paracrine regulation, but the dependence on gonadotrophins starts in fetal life. During maturation of the hypothalamic-pituitary-testicular axis, the target organs acquire their responsiveness (viz receptors) before the onset of secretion of the tropic hormonal stimulus. The last link to develop is the feedback regulation, and the whole axis is functional in the developing male rat during the last days of gestation. Although gonadotrophin secretion starts in both sexes simultaneously, the fetal ovary is endocrinologically quiescent--its gonadotrophin responsiveness and endocrine activity begin only after birth. The fetal and postnatal periods of testicular activity have crucial effects on male sexual differentiation, whereas in the female, early sexual development occurs autonomously without influence of ovarian function. The purpose of this review is to elucidate some of the recent findings on the molecular mechanisms involved in the perinatal maturation of the rat hypothalamic-pituitary-gonadal axis.

Effects of gonadotrophin deprivation on follicular growth in gilts

The endocrine and ovarian effects of hypophysectomy (n = 5) and gonadotrophin-releasing hormone (GnRH) antagonist administration (Antarelix) (n = 5) were studied in gilts by comparison with control animals (n = 6). All gilts were given Regumate (20 mg/d for 18 d). The last day of Regumate was day 0. Hypophysectomy and initiation of Antarelix administration (0.6 mg iv twice daily for 7 d) were performed on day 5. All ovaries were obtained at slaughter on day 12. Blood samples were obtained daily from all Antarelix-treated and control sows to measure luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations. Frequent sampling was performed on day 10 on control and Antarelix-treated gilts to assess pulsatile LH secretion. Oestrus or LH surge was initiated before the beginning of treatment in 2 hypophysectomized, 4 Antarelix-treated, and 4 control females. Gonadotropins were undetectable in the blood of hypophysectomized sows on day 6. On day 10, pulsatile LH release was blocked in Antarelix-treated gilts. At no time were FSH concentrations significantly affected. Histological observation of the ovaries demonstrated that: (i) similar populations of healthy or total (healthy + atretic) follicles < 1 mm were found in the 3 groups of females; (ii) healthy follicles 1 to 2 mm in diameter were present in Antarelix-treated but not in hypophysectomized gilts; and (iii) healthy follicles > 2 mm were absent in Antarelix-treated and hypophysectomized gilts. The present study suggests the existence of 3 subgroups amongst antral follicles (gonadotropin independent: 0.19 to 1.1 mm; FSH dependent: 1.1 to 2 mm; LH pulses dependent: > 2 mm in diameter).

Development and influence of an endogenous serum luteinizing hormone surge after ovulation induction in stimulated cycles

The aim of this study was to investigate whether the endogenous serum luteinizing hormone (LH) discharge in stimulated cycles--either simultaneously with or shortly after exogenous human chorionic gonadotropin (hCG) administration--is influenced by serum steroid hormones and follicle stimulating hormone (FSH). We also tested whether the LH discharge affects intrafollicular hormone metabolism and oocyte fertilization. In a group of 46 women with tubal pathology who were undergoing in vitro fertilization (IVF), follicular fluids were collected during oocyte retrieval. In addition blood samples were drawn daily, starting at cycle day 7 until the day of oocyte retrieval. LH, FSH, estradiol, progesterone, testosterone and prolactin were determined in all samples of serum and follicular fluid. Oocyte maturation was classified according to the morphology of the oocyte corona-cumulus complex. Of the 46 women studied, 15 showed no LH surge (group A) and 31 developed an endogenous LH surge (group B). Serum samples showed no significant differences between the two groups in follicular phase estradiol, progesterone, testosterone and prolactin. Only levels of serum FSH showed a significant difference between groups A and B (p < 0.0005). In follicular fluid samples LH (p < 0.05) and FSH levels (p < 0.005) were significantly different. Fertilization rate and cleavage rate, however, did not differ significantly. The late endogenous LH surge occurring simultaneously with or shortly after hCG application for ovulation induction did not affect intrafollicular steroid metabolism, oocyte maturation, fertilization rate or cleavage rate.

[IGF(s) and testicular functions. Secretion and action of IGF-1 on Leydig cells]

Many in vitro and in vivo studies have demonstrated a presence of IGF-I in the testis. Testicular production of IGF-I and its mRNA is stimulated largely by gonadotropins; FSH acts on Sertoli cells while LH acts on Leydig cells. A regulation by local factors is also demonstrated; the role of GH remains unclear. In the testis, IGF-I has various effects but we only focussed this review on Leydig cells. Specific receptors have been characterized on these cells. They are up-regulated by LH/hCG (at the transcriptional level) and down regulated by IGF-I. The effect of GH is depend on the experimental models used. In addition in this paper, we have shown in adult rats that the IGF-I level in the testicular interstitial fluid and the IGF-I receptors on Leydig cells are modified by fasting. Both in vivo and in vitro, IGF-I increased LH/hCG receptors and the steroïdogenic response to hCG by a mechanism which is poorly understood yet.

[Role of IGF system in the ovary]

The stimulating effect of Insulin-like Growth Factors (IGFs) on ovarian folliculogenesis is modulated by binding proteins (IGFBPs). During follicular growth, levels of IGFBP-2, -4 and -5 decrease in follicular fluid. These changes are a consequence of a decrease in synthesis and of a degradation by gonadotropin-stimulated specific proteases. They lead to an increase in the bioavailability of IGFs and their action on granulosa cells. By contrast, follicular atresia is characterized by a high increase in the synthesis and levels of IGFBPs < 40kDa, and by a dramatic decrease in IGFs bioavailability. Finally, at least part of intrafollicular IGFs and IGFBP-3 may be derived from the circulatory pool. Their levels only change slightly during follicular growth and atresia.