Follicle-stimulating hormone increases guanine nucleotide-binding regulatory protein subunit alpha i-3 mRNA but decreases alpha i-1 and alpha i-2 mRNA in Sertoli cells

FSH interacts with a guanine nucleotide-binding protein (G-protein)-coupled receptor, which in turn modulates signal transduction via the G-protein subunit alpha s. However, it is unknown whether FSH regulates alpha-subunit gene expression and whether G-protein alpha-subunit genes other than alpha s are modulated in FSH-stimulated signal transduction. Regulation of mRNA for alpha s and alpha i-2 was studied in primary cultures of rat Sertoli cells because these proteins are linked to the control of adenylyl cyclase. In addition, mRNA for alpha i-1 and alpha i-3 were quantified because these proteins are putatively linked to ion channels but have not been well characterized in the Sertoli cell. Northern blot analyses demonstrated that FSH induced a dose-dependent increase in steady state levels of alpha i-3 mRNA. In contrast, FSH caused a dose-dependent decrease in levels of alpha i-1 and alpha i-2 mRNA. No significant effect of FSH on alpha s mRNA levels was detectable. The time course of FSH effects showed a 75% decrease in alpha i-1 mRNA levels, a 50% decrease in alpha i-2 mRNA levels and a nearly 3-fold increase in levels of alpha i-3 mRNA between 4-6 h of treatment with 100 ng/ml FSH. Steady state levels of alpha i-1 and alpha i-2 mRNA returned to pretreatment levels after 10 h FSH treatment, while alpha i-3 mRNA returned to a new steady state level approximately 50% greater than the pretreatment level.(ABSTRACT TRUNCATED AT 250 WORDS)

Mediation of gonadotrophin-stimulated growth and differentiation of human granulosa cells by adenosine-3',5'-monophosphate: one molecule, two messages

OBJECTIVE

To determine how the second messenger adenosine-3',5'-monophosphate (cyclic AMP) is able to mediate divergent actions of FSH and LH on granulosa cell growth and differentiation in human ovaries.

DESIGN

Human granulosa cells were cultured for 96 hours in serum-free medium 199 containing increasing doses of either FSH, LH or dibutyryl cyclic AMP. Extra and intra-cellular cyclic AMP levels were determined by radioimmunoassay. Tritiated thymidine uptake and cell number were measured as indices of cell growth, and spent medium was assayed for steroids (oestradiol and progesterone) to reflect differentiation.

PATIENTS

'Mature' granulosa cells were aspirated from preovulatory follicles in the ovaries of clomiphene-stimulated patients undergoing laparoscopic sterilization; 'luteinized' granulosa cells were aspirated from periovulatory follicles in the ovaries of gonadotrophin-stimulated in-vitro fertilization patients.

RESULTS

LH consistently inhibited, whereas FSH maintained or stimulated, basal granulosa cell numbers. Steroidogenesis was dose-dependently increased by both gonadotrophins, with LH having the significantly greater effect over the entire dose-response range (1-100 micrograms/l). LH also induced significantly more cyclic AMP production than FSH, both intra and extra-cellularly, providing a basis for differential post-receptor signalling via a common second messenger. Addition of dibutyryl cyclic AMP, at low concentrations (10-250 mumol/l) to the cultured cells in the absence of gonadotrophins mimicked FSH effects with stimulation/maintenance of cell numbers and moderate steroidogenesis. High concentrations of dibutyryl cyclic AMP (500-1000 mumol/l) caused a significant inhibition of cell numbers together with maximal steroidogenesis, simulating LH action.

CONCLUSIONS

These results suggest that granulosa cell maturation in the follicular phase of the menstrual cycle (controlled by FSH) is associated with a low cyclic AMP tone that favours cell growth and expression of aromatase activity in the developing preovulatory follicle. During the early luteal phase (dominated by LH), the intracellular cycle AMP tone increases to allow maximal progesterone production and inhibition of cell growth in the corpus luteum. Thereby one second messenger can mediate divergent gonadotrophic effects on granulosa cell growth and differentiation in the human ovary.

Molecular basis of gonadotrophin action on human granulosa cell function

We studied in vitro the effects of Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH) on: 1) mature human granulosa cell proliferation and steroidogenesis; 2) intra-cellular second messenger (cAMP) generation, and the effects of cAMP analogues on cell function; and 3) mRNA expression of the rate limiting enzymes for progesterone and oestradiol synthesis namely: Cholesterol side chain cleavage (P450 SCC), Aromatase (P450 Arom); and 4) LH receptor mRNA expression. FSH maintained or stimulated, whereas LH markedly inhibited, basal granulosa cell proliferation. Steroidogenesis (oestradiol and progesterone production) was dose dependently increased by both gonadotrophins; with LH having the greater effect. However, only LH was able to induce maximal progesterone production. FSH generated about ten fold less cAMP than LH; and low and high doses of cAMP analogue were able to mimic FSH and LH effects respectively. Northern analyses showed that both FSH and LH were able to induce maximal P450 Arom mRNA expression, whereas only LH could stimulate maximal P450 SCC mRNA transcription. Maximal P450 Arom mRNA expression was associated with less cAMP generation than for P450 SCC. LH-R mRNA expression was induced by FSH but the strongest stimulatory effect was with LH. These results indicate that: 1) FSH and LH have markedly different effects on mature granulosa cell function; 2) the differential action of FSH and LH are dose dependently mediated through intracellular cAMP; 3) mRNA expression of P450 SCC and P450 Arom are differentially regulated by gonadotrophins and intracellular cAMP; and 4) LH was the most potent inducer of its own receptor mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Hormonal regulation of messenger ribonucleic acid encoding a novel isoform of prostaglandin endoperoxide H synthase in rat preovulatory follicles. Induction in vivo and in vitro

Recent purification and amino-terminal analysis of the isoform of prostaglandin endoperoxide H synthase (PGS) induced in rat preovulatory follicles by gonadotropins identified it as a novel distinct isoform of PGS (rPGSi) which exhibited a high degree of homology to the deduced sequence of PGS-related cDNAs recently cloned in chicken and mice. To further verify the similarities of these novel gene products and to examine the hormonal regulation of rPGSi mRNA in ovarian cells, three different in vivo and in vitro models were used. Northern blots using a cDNA encoding the mouse homologue of rPGSi detected a 4.4-kilobase transcript which was rapidly but transiently induced in granulosa cells of preovulatory follicles exposed in vivo to an ovulatory dose of human chorionic gonadotropin. The rPGSi mRNA was undetectable at 0 h, peaked 4 h after human chorionic gonadotropin, and had almost disappeared by 6 h. Increases in rPGSi protein (immunoblots) lagged by about 1 h, peaked at 5 h, and remained present at 11 h. PGSi mRNA and protein were also induced in a time- and dose-dependent manner when preovulatory follicles were isolated and incubated with elevated levels of follicle-stimulating hormone (500 ng/ml) or luteinizing hormone (500 ng/ml), or when differentiated granulosa cell cultures were stimulated with follicle-stimulating hormone, luteinizing hormone, or with gonadotropin-releasing hormone (10(-6) M). In both in vitro systems, rPGSi mRNA peaked at 4-5 h. When the same RNA samples were probed with the mouse cDNA encoding the other PGS isoform, no mRNA transcripts (2.8 kilobases) were observed. These results show for the first time that a rapid and transient induction of mRNA encoding a novel PGS enzyme occurs in granulosa cells of preovulatory follicles prior to ovulation and that results in vitro closely mimicked those in vivo and thereby provide models for studying the molecular mechanisms of rPGSi gene expression.

Biochemical factors involved in the FSH action on amino acid transport in immature rat testes

Testes of 15-day-old rats preincubated and incubated during different times with various doses of FSH (0.2; 2.0 and 20.0 mU/ml) in Krebs-Ringer bicarbonate (KRb) buffer increase the uptake of [14C] methylaminoisobutyric acid and [14C] aminoisobutyric acid. The basal and FSH stimulated amino acid transport occurs at absolute lower levels when the protein or glycoprotein synthesis is inhibited by cycloheximide (350 mumol/l) or tunicamycin (12 mumol/l) or when the microtubules are depolymerized with colchicine (1.2 mumol/l). However, the proportional increase of amino acid transport produced by FSH was maintained. The blockage of the voltage-dependent Ca++ channels with verapamil or the competitive inhibition of the bivalent ion channels by Co++ or Ni++ nullified the stimulatory action of FSH on the amino acid transport. Also quinine, that blocks the ATP dependent K+ channels, abolished the FSH action. It was concluded that in immature rat testes FSH stimulates amino acid transport through a mechanism involving voltage-dependent Ca++ channels and ATP-sensitive K+ channel.

Developmental capacity of mouse oocytes matured in vitro: effects of gonadotrophic stimulation, follicular origin and oocyte size

Development of mammalian oocytes is usually correlated with ovarian follicular development. This correlation was tested by determining whether gonadotrophic stimulation of follicular development in immature mice resulted in a coordinated increase in the embryonic developmental capacity of the oocytes. Oocyte cumulus cell complexes were isolated at the germinal vesicle stage from small, medium and large antral follicles of 26-day-old mice and matured and fertilized in vitro. The frequency with which embryos from oocytes from small follicles completed the two-cell to blastocyst transition was lower than for embryos from oocytes from large follicles (33% and 79%, respectively). Germinal-vesicle stage oocyte-cumulus cell complexes were isolated from 22-26-day-old mice that were unprimed or primed by injection of equine chorionic gonadotrophin 48 h before isolation. Oocytes were matured in control medium, or in medium containing 1 microgram follicle-stimulating hormone (FSH) ml-1, and then fertilized in vitro. Priming did not increase the number of embryos completing the two-cell stage to blastocyst transition in the 22-day-old group nor did FSH treatment of maturing oocytes when the oocytes were isolated from unprimed 22-day-old mice. In contrast, priming increased the percentage of embryos completing the two-cell stage to blastocyst transition in the 26-day-old group by 20%. FSH treatment of maturing oocytes from the unprimed, 26-day-old group increased the number of embryos completing the transition to the same level as those in the primed 26-day-old group, but FSH did not increase the frequency of transition in the primed 26-day-old group.(ABSTRACT TRUNCATED AT 250 WORDS)

Basal and FSH-stimulated steady state levels of SGP-2, alpha 2-macroglobulin, and testibumin in culture media of rat seminiferous tubules at defined stages of the epithelial cycle

Production of several proteins by rat Sertoli cells is dependent on the stage of the cycle of the seminiferous epithelium. The authors have determined steady state levels and follicle-stimulating hormone responsiveness of three Sertoli cell products in culture media of rat seminiferous tubule segments at different stages of the epithelial cycle: SGP-2 (sulfated glycoprotein-2), alpha 2-macroglobulin, and testibumin. Basal SGP-2 levels were twofold higher in stages VII through VIII compared with stages XIII to I to VI (P less than 0.05). Highest basal alpha 2-macroglobulin levels were found in stages II through VIII; this was about 35% greater than in stages XIII through I of the cycle (P less than 0.05). Basal testibumin levels were twofold higher in stages II through VI compared with stages IX through XII of the cycle. Follicle-stimulating hormone had no effect on SGP-2, but by contrast it (50 mg/L) increased the level of alpha 2-macroglobulin significantly (P less than 0.05) in stages XIII through I. Follicle-stimulating hormone treatment (10 mg/L) elevated testibumin levels at each stage-pool by about 40% (P less than 0.05). The current results using staged tubular segments in vitro demonstrate cyclic basal steady-state levels of the three proteins along the seminiferous tubules and follicle-stimulating hormone regulation of alpha 2-macroglobulin and testibumin.

The physiology of testicular inhibin and related proteins

The roles of inhibin and related proteins in the male remain unclear, although it is becoming increasingly evident that they play a part in FSH regulation and testicular function, including spermatogenesis. The difficulties associated with these questions have been the limited availability of inhibin and related proteins for in vivo studies, the absence of specific assay methods, and the unclear relationship of inhibin and testosterone in the regulation of FSH secretion. With the availability of human recombinant preparations and the current development of new assays, it is anticipated that many of these questions will be resolved.

Mechanism of ovulation

This article provides a fundamental basis for a better understanding of normal ovarian physiologic processes relevant to the pathophysiology of ovarian dysfunction and the treatment of infertility. The discussion centers on the pelvic clock, which regulates by steroidal and nonsteroidal endocrine and paracrine messages both hypothalamic-pituitary and intraovarian functions essential to successful reproduction, and the steroidal milieu that generates the approximately 28-day human menstrual cycle.

An antipodean perception of the mode of action of glycoprotein hormones

Continuance of vertebrate species and maintenance of metabolism have an absolute requirement for the glycoprotein hormones of the anterior pituitary gland. It is now firmly accepted that the N-glycans of these and the related placental hormone, chorionic gonadotropin, have essential if undefined roles in their mechanism of action. However, recent investigations by Weisshaar and his colleagues on the oligosaccharides of human luteinizing hormone and chorionic gonadotropin, do not support the generally accepted view of carbohydrates in hormone-receptor interactions and a further concept is proposed that invokes negative charges and changes in structured water.

FSH isoforms, radioimmunoassays, bioassays, and their significance

Follicle-stimulating hormone (FSH) plays a central role in steroidogenesis and gametogenesis. In recent years, a great deal has been learned about the microheterogeneity of FSH using newly developed assay techniques. This review article will attempt to discuss the advantages and the limitations of recently developed and commonly used assay systems.

Time of ovulation in merino ewes superovulated with PMSG and FSH-P

An experiment examined the effects of treatment with gonadotrophin releasing hormone (100 micrograms GnRH injected 24 h after progestagen sponge removal), season of treatment (autumn v. spring), the effect of supplementary feeding with lupin grain (in autumn only, from 12 days before until 8 days after sponge removal) on the time of ovulation in 182 mature Merino ewes superovulated with a combination of 400 I.U. pregnant mare serum gonadotrophin (PMSG) and 12 mg follicle stimulating hormone (FSH-P). Time of ovulation was influenced by both season and the administration of GnRH. Two peaks of ovulation were observed in spring, the first between 24 and 30 h after sponge removal, and the second commencing 42 h after sponge removal. In autumn, there was one peak of ovulation between 42 and 54 h after sponge removal. Treatment with GnRH advanced the time of ovulation in autumn (P less than 0.05), but had no apparent effect in spring. In contrast to the effect of GnRH, time of ovulation for ewes treated in autumn was delayed (P less than 0.001) by supplementary feeding with lupins.

Mechanism of reproductive deficiency in spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR) show multiple endocrine disorders. In the present work, specific reproductive modifications were analysed using normotensive Wistar-Kyoto rats (WKY) as controls. SHR showed delayed vaginal opening and first estrus presentation, regular vaginal cycles and released a normal number of ova each cycle. When compared with controls, SHR showed a decrease in the percentage of successful pregnancies (69% vs. 86% in WKY) and in the litter size (7.83 +/- 0.5 vs. 10.41 +/- 0.5). In SHR, progesterone plasma levels were significantly increased during the days 1-14 of pregnancy, and on the 5th day of pregnancy the plasma concentrations of LH but not of FSH were enhanced. Mortality during the first month of life was higher in SH (50%) than in control (24%) strain. When the SH females were mated with Wistar or WKY males, the percentage of pregnancies rose up to 95%. On the contrary, Wistar or WKY females mated with SH males showed a decrease in the percentage of pregnancies (62.5% and 50%, respectively). Besides, the litter sizes were significantly reduced in Wistar females mated with SH males. Newborn SH suckled immediately after birth from a WKY mother showed a significant reduction in the mortality during the first month of life (8% vs. 50%). In conclusion, our results suggest that changes in fertilization and/or implantation processes of SH rats were responsible for the reduced pregnancy rate, whereas the increased neonatal mortality could be due to lactation activity of SH mothers.

Control of inhibin production by dispersed human luteal cells in vitro

The production of inhibin in vitro by dispersed cells from early to mid (Days 16-19) and late stage (Day 23) human corpus luteum (CL) was examined, and the effects of human chorionic gonadotrophin (hCG), follicle stimulating hormone (FSH), oestradiol and testosterone on inhibin production were determined. Corpora lutea from five subjects in the early to mid luteal stage and three subjects in late luteal stage were dispersed with enzymes and the luteal cells cultured in medium supplemented with 5% calf serum and either FSH (1, 10 or 100 ng mL-1), oestradiol-17 beta (2.5, 5 or 10 micrograms mL-1) or testosterone (0.25, 1 or 5 micrograms mL-1) with or without hCG (1 I.U. mL-1). Cells were cultured for 1 to 3 days without changes of medium, and the concentrations of progesterone, oestradiol and immunoreactive inhibin in the medium were measured by radioimmunoassay. Cells from both types of CL produced inhibin in vitro under basal conditions, but only cells from early to mid CLs responded to hCG with a significant increase in inhibin production. Both progesterone and oestradiol production were stimulated by hCG in both groups of CL. Inhibin concentrations in the cell cultures declined with time in culture, particularly in the late CL group, whereas the concentration of steroids increased. Neither FSH, oestradiol nor testosterone significantly changed inhibin production in either CL group. It was concluded that inhibin production by human luteal cells in vitro is influenced by the age of the CL, and is dependent on LH (hCG) but not on FSH or sex steroids.

Hormonal regulation of gonadotropin receptor mRNA in rat ovary during follicular growth and luteinization

To investigate the regulation of the follicle-stimulating hormone (FSH) and luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptor genes by gonadotropins, we examined the effect of pregnant mare's serum gonadotropin (PMSG) or PMSG-hCG on the expression of FSH and LH/hCG receptors in rat ovaries. After administration of PMSG, Northern blot analysis using the FSH receptor cDNA probe revealed that a major band of 2400 nucleotides was detected which reached the maximal level on day 3. On the other hand, the level of LH/hCG receptor mRNA, a major mRNA of 5400 nucleotides and minor species of 7500, 3600, 2300 and 1200 nucleotides, increased progressively during 4 days. Treatment with hCG resulted in a decrease of FSH and LH/hCG receptor mRNA levels, and the level of FSH receptor mRNA was completely suppressed. Although the level of LH/hCG receptor mRNA was also suppressed from 3 h to an almost undetectable level at 24 h after hCG injection, it recovered to the control level by 48 h and exceeded this level several fold by 72 h. The reappearance of LH/hCG receptors following desensitization was preceded by an increase in mRNA levels. These studies demonstrate that hormonal regulation of gonadotropin receptor mRNAs on rat ovary reflects the changes in gonadotropin receptor levels.

Comparative in vitro and in vivo studies on the biological characteristics of recombinant human follicle-stimulating hormone

The in vitro and in vivo activities of recombinant human FSH (recFSH) produced by a Chinese hamster ovary cell line were studied and compared with those of natural FSH preparations. The specific FSH activities of recFSH established by immunoassay and in vivo bioassay were greater than 10,000 IU/mg protein and considerably higher than the activities of tested urinary FSH references, while the in vivo bio/immuno ratios of these preparations were not significantly different. Compared to a highly purified pituitary standard (IS 83/575), recFSH had a comparable high specific in vivo bioactivity, but the specific immunoreactivity of IS 83/575 was about 2 times lower. In receptor displacement and in vitro bioassay studies recFSH provided dose-response curves parallel to those of pituitary and urinary FSH references. When equal amounts of immunoreactivity FSH were tested, recFSH and urinary and pituitary FSH displayed comparable activities in both assays. The in vitro bioactivity of recFSH could be neutralized effectively by each of three monoclonal antibodies raised against recFSH (alpha-specific), urinary FSH (beta-specific), and pituitary FSH (alpha beta-specific), respectively. Moreover, 50% inhibition of comparable responses induced by recFSH, urinary "pure" FSH, or pituitary FSH was established by the same amount of monoclonal antibody. These results support the structural and functional similarity of recFSH and natural FSH. To test whether recFSH is capable of inducing LH-specific biological responses, the in vitro induction of testosterone production in mouse Leydig cells was assessed. At least 16 IU recFSH/ml incubate were needed to increase testosterone production, indicating that the intrinsic LH bioactivity of recFSH is negligible (less than 0.025 mIU LH/IU FSH). The in vivo efficacy of recFSH was examined by treating immature female hypophysectomized rats during 4 days with recFSH only or with recFSH supplemented with hCG. RecFSH only treatment increased ovarian weight and aromatase activity in a dose-dependent manner. When recFSH dosages providing submaximal responses were supplemented with 1 IU hCG, both ovarian weight and aromatase activity were largely augmented. Neither recFSH nor urinary pure FSH, administered in a high dose was able to increase plasma estradiol levels, while ovarian weight and aromatase activity were increased to the same extent. However, when recFSH was supplemented with only 0.1 IU hCG, a 3-fold increase in median plasma estradiol levels was obtained. These findings support the two-cell two-gonadotropin theory, holding that both FSH and LH are required for estrogen biosynthesis, but also reveal that only very small amounts of LH activity are sufficient to increase estrogen secretion up to measurable plasma levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of cyclic AMP and phorbol ester on transepithelial electrical resistance of Sertoli cell monolayers in two-compartment culture

The effects of dibutyryl cyclic AMP [Bu)2cAMP) and phorbol ester (TPA), in the absence or presence of follicle-stimulating hormone (FSH) and/or testosterone, on the development of tight junctions by immature rat Sertoli cells (Sc) were investigated in vitro using the two-compartment culture system. The tight junction status was evaluated by repeated measurements of transepithelial electrical resistance (TER). Untreated cell monolayers developed stable TER of approximately 120 omega cm2 during 3 days of culture. Continuous presence of FSH (200 ng/ml) from day 1 onward significantly increased the TER up to approximately 300 omega cm2 after a transient (24-36 h) delay. The initial delay was prolonged to 3-4 days by the addition of 1-methyl-3-isobutylxanthine (MIX) (0.2 mM), whereas the subsequent increase of TER was significantly potentiated by the concomitant presence of testosterone (10 microM). Cholera toxin (CHT; 10 ng/ml) and forskolin (FR; 50 microM) mimicked these FSH effects. (Bu)2cAMP, at concentrations which maximally stimulated immunoactive inhibin secretion (100-500 microM), inhibited the initial TER increase and significantly decreased the TER level when added on days 1 and 5 of culture, respectively. In contrast, low concentrations of (Bu)2cAMP (4-20 microM) consistently stimulated the TER development, mimicking the stimulatory phase of FSH action. TPA (100 nM) alone had no effect on TER development, but potentiated the stimulatory effect of testosterone in a manner similar to FSH, CHT, FR or low concentrations of (Bu)2cAMP. These results demonstrate, for the first time, a concentration-dependent, dual effect of exogenous cAMP on the Sc function.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of Chronogest implants and Folltropin for estrus synchronization and superovulation in goats

Six Barbari goats each were assigned randomly to treatments 1,2 or 3, comprising im injections of FSH (folltropin) at 12, 14 or 16 mg dose level respectively. Estrus was synchronized with intravaginal sponge impregnated with flugestone acetate (30 mg; chronogest) inserted for 12 days and cloprostenol (125 micrograms) im at the insertion as well as at removal of sponge. FSH treatment started 48 hr before the sponge removal as 4-day declining dose scheme. Estrus could be effectively synchronized in all goats under the study, with significant difference (P less than 0.05) in the onset of estrus between the treatment groups. All goats were administered with 750 IU hCG i.v. at estrus. Recording of ovarian response and embryo recovery was done 45 hr after the onset of estrus. The prime aim of superovulation was effectively achieved in Barbari goats with the use of chronogest implants and folltropin. There was no difference (P greater than 0.05) between the treatment groups in recovery of transferable embryos, however, 14 mg folltropin appeared to be near optimal dose. There was no adverse effect on the quality of recovered embryos with high doses of folltropin.

Effect of specific FSH or LH deprivation on testicular function of the adult rat

While the need for FSH in initiating spermatogenesis in the immature rat is well accepted, its requirement for maintenance of spermatogenesis in adulthood is questioned. In the current study, using gonadotropin antisera to neutralize specifically either endogenous FSH or LH, we have investigated the effect of either FSH or LH deprivation for a 10-day period on (i) testicular macromolecular synthesis in vitro, (ii) the activities of testicular germ cell specific LDH-X and hyaluronidase enzymes, and finally (iii) on the concentration of sulphated glycoprotein (SGP-2), one of the Sertoli cell marker proteins. Both immature (35-day-old) and adult (100-day-old) rats have been used in this study. Since LH deprivation leads to a near total blockade of testosterone production, the ability of exogenous testosterone supplementation to override the effects of LH deficiency has also been evaluated. Deprivation of either of the gonadotropins significantly affected in vitro RNA and protein synthesis by both testicular minces as well as single cell preparations. Fractionation of dispersed testicular cells preincubated with labelled precursors of RNA and protein on Percoll density gradient revealed that FSH deprivation affected specifically the rate of RNA and protein synthesis of germ cell and not Leydig cell fraction. LH but not FSH deprivation inhibited [3H]thymidine incorporation into DNA. The inhibitory effect of LH could mostly be overriden by testosterone supplementation. LDH-X and hyaluronidase activities of testicular homogenates of adult rats showed significant reduction (50%; P less than .05) following either FSH or LH deprivation. Again testosterone supplementation was able to reverse the LH inhibitory effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Reevaluation of the roles of luteinizing hormone and follicle-stimulating hormone in the ovulatory process

Circulating levels of luteinizing hormone (LH) are essential for the production of steroid hormones that regulate the timing of ovulation and target tissue responses, as well as maintenance of the corpus luteum and therefore early pregnancy. Clinical and basic science observations show that elevated levels of serum LH during the follicular phase of the menstrual cycle are not only unnecessary for follicular maturation but are deleterious to normal reproductive processes. These elevations may occur as a result of administration of exogenous LH or through an endogenous pathological process (i.e. polycystic ovarian disease, PCOD). Resting levels of LH, synergizing with locally produced IGFs, inhibin and perhaps other growth factors, are adequate for normal follicular growth and steroidogenesis. Elevations in serum LH above these resting levels may result in increased androgen production that diminishes follicular function and reduces early embryo viability. Elevated LH levels during the preovulatory period may also negatively influence post-ovulatory events such as conception and implantation. With these facts in mind, the best results for ovulation induction would be expected with purified follicle-stimulating hormone (FSH) administration to women following gonadotrophin releasing hormone (GnRH) down-regulation. It is hoped that this review provides the reader with an analysis of the complex series of events that regulate normal follicular maturation. The reevaluation of the two cell-two gonadotrophin theory suggests that during the preovulatory period, resting levels of LH are adequate for normal follicular maturation. Indeed, overstimulation of the ovary with excessive amounts of LH may diminish the ability of that target organ to produce fertile ova.(ABSTRACT TRUNCATED AT 250 WORDS)

Properties and hormonal regulation of two structurally related cAMP phosphodiesterases from the rat Sertoli cell

Upon exposure to follicle-stimulating hormone (FSH), the gonadotropin-responsive Sertoli cell expresses increased rolipram-sensitive cAMP-specific phosphodiesterase (cAMP-PDE) activity. To understand the mechanisms leading to this activation, the cAMP-PDEs present in the Sertoli cell were characterized and their regulation studied. Comparison of the conceptual translates of two groups of PDE cDNA clones isolated from a Sertoli cell cDNA library (ratPDE3 and ratPDE4) showed that the encoded proteins were structurally similar, containing a core region of 455 amino acids with a sequence identity of 87%. The amino and carboxyl termini were divergent. Expression of these cDNAs in Escherichia coli and monkey COS-7 cells demonstrated that the encoded cAMP-PDEs had similar affinities for the cAMP substrate and were equally sensitive to a number of PDE inhibitors (rolipram greater than Ro 20-1724 greater than cilostamide). FSH stimulation of the Sertoli cell produced an increased rate of transcription of the ratPDE3 gene and elevated mRNA levels for ratPDE3 and to a lesser extent of ratPDE4. The increase in mRNA levels was detected after 1 h of stimulation. Forskolin, cholera toxin, and N6, O2'-dibutyryl cAMP produced a similar increase in rate of transcription and elevated mRNA levels, indicating that this activation is mediated by an increase in intracellular cAMP. RatPDE4 mRNA levels were maximal upon exposure to 10 ng of FSH/ml, whereas ratPDE3 mRNA levels could be further elevated, with higher FSH concentrations. The intensity of an immunoreactive band with characteristics identical to a purified cAMP-PDE, correlated with the increased cAMP hydrolytic activity after FSH or dibutyryl cAMP treatment, demonstrating that changes in cAMP-PDE protein levels are involved in this regulation. These data provide evidence that multiple cAMP-PDE forms are expressed in the rat Sertoli cell. Although differences in the pattern of activation of these forms were observed, these data show, that in the rat Sertoli cell, the cAMP-PDE activity is regulated by hormones via a novel mechanism that involves a cAMP-dependent activation of transcription of a PDE gene.

Follicle-stimulating hormone increases c-fos mRNA levels in rat granulosa cells via a protein kinase C-dependent mechanism

Recent evidence has been presented that follicle-stimulating hormone (FSH) stimulates the induction of granulosa cell c-fos protooncogene mRNA in vivo (Pennybacker and Herman (1989) J. Cell Biol. 109, 151A; Delidow et al. (1990) Endocrinology 126, 2302-2306), yet the mechanisms by which FSH induces c-fos mRNA expression have not been delineated. To elucidate the mechanisms of FSH-dependent c-fos mRNA expression, we measured the time and dose dependence of c-fos mRNA levels using Northern blot analysis in intact ovaries and cultured granulosa cells in response to FSH. In intact ovaries, FSH-induced c-fos mRNA expression was time dependent with maximal expression at 90 min post FSH injection, while in cultures of granulosa cells obtained from estrogen-primed immature female rats, c-fos mRNA levels were highest after 30 min exposure to FSH and at a concentration of 100 ng/ml. Neither 8-bromo adenosine 3',5'-cyclic monophosphate (8-br-cAMP), at doses ranging from 0.1 to 10 mM, nor 100 microM forskolin (in the presence or absence of 200 microM isobutyl-methylxanthine) or luteinizing hormone (LH, 100 ng/ml) were able to mimic FSH-induced c-fos mRNA expression in granulosa cell cultures. However, tetradecanoyl-13-phorbol acetate (TPA, 200 nM) was able to induce c-fos mRNA expression. The protein kinase C (PKC) inhibitors H-7 (0.3-30 microM) and staurosporine (0.75 micrograms/ml) blocked FSH-induced c-fos mRNA expression in cultured granulosa cells while HA 1004, an inhibitor of cGMP- and cAMP-dependent protein kinases at 30 microM had no effect on TPA-induced c-fos expression, and only minimally inhibited FSH-induced c-fos expression. Both FSH (100 ng/ml) and forskolin (3 microM) increased progesterone production in cultured granulosa cells. These data support the hypothesis that FSH specifically induces c-fos mRNA expression by a PKC-dependent mechanism and that the cAMP arm of the FSH response pathway is operant in these cells.