Urinary concentrations of ovarian steroid hormone metabolites and bioactive follicle-stimulating hormone in killer whales (Orcinus orchus) during ovarian cycles and pregnancy

Reproductive hormone profiles of six captive killer whales (Orcinu orcus) from three Sea World aquaria were studied for intervals up to 2 yr. Daily urine samples and bimonthly blood samples were collected and analyzed for hormone concentration. Immunoreactive estrone conjugates, pregnanediol-3-glucoruonide, 20-alpha-hydroxyprogesterone as well as bioactive follicle-stimulating hormone (FSH) were measured in urine samples and indexed by creatinine concentrations of the same sample. In selected cases, serum progesterone concentrations were also measured. Three of the animals in the study became pregnant during the study period and two of these animals were evaluated during the time of conception and throughout most of gestation. From the data of the three animals that conceived, hormone profiles of the complete ovarian cycle, early pregnancy, and mid- to late gestation are described. The remaining three animals did not conceive and only one of these demonstrated hormone changes that indicated regular ovarian activity. The female reproductive pattern of the killer whale is characterized by a gestation of 17 mo and an ovarian cycle of 6-7 wk in duration. The hormone changes associated with the ovarian cycle of the killer whale are similar to those of most other mammalian species. A bimodal pattern of bioactive FSH with a pronounced rise of estrogen predominates the preovulatory hormone profile. After ovulation, increased progesterone production is observed for approximately 4 wk in the nonconceptive ovarian cycle. During the luteal phase and early pregnancy, when progesterone metabolites are elevated, estrogen metabolite excretion remains low. These data extend the application of urine collections for longitudinal studies involving hormone changes, particularly those involving nondomesticated species.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibroblast growth factor inhibits luteinizing hormone-stimulated androgen production by cultured rat testicular cells

The effect of fibroblast growth factor (FGF) on LH-stimulated testosterone production was investigated using primary cultures of rat testicular cells. Testicular cells obtained from neonatal rats (8-9 days of age) were maintained in culture for 3 days and then challenged with LH with or without basic FGF. After 3 additional days of culture, the media were collected for steroid RIA. LH treatment of cultured cells stimulated testosterone production in a dose-dependent fashion whereas FGF alone did not affect androgen biosynthesis. In contrast, cotreatment with FGF caused a dose-dependent decrease of LH-stimulated testosterone production, with an IC50 value of 1.1 X 10(-9) M (as calculated from three separate experiments). The inhibitory effect of FGF was evident 24 h after the initiation of treatment and this effect was reversible 1 day after the cessation of FGF treatment. The inhibition of LH-induced testosterone production by FGF (maximal inhibition greater than 90%) was accompanied by a 12-fold increase in progesterone levels, suggesting that the inhibitory effect of FGF was distal to the step of progesterone formation. FGF also inhibited forskolin (10(-5) M)- and (Bu)2cAMP (5 X 10(-4) M)-stimulated testosterone production. Furthermore, FGF inhibited the conversion of exogenously added androgen precursors (progesterone and 17 alpha-hydroxyprogesterone) to testosterone in LH-stimulated cultures indicating that FGF might inhibit 17 alpha-hydroxylase activity. The concept of a direct testicular action of FGF was further supported by the demonstration of high affinity (Kd: 3.9 X 10(-10) M; n = 3 experiments) and low capacity (46,900 sites per cell) FGF receptors in cultured testis cells. The binding of [125I]FGF was inhibited by basic and acidic FGF but not by several other growth factors. In conclusion, we suggest that FGF binds to testicular cells and inhibits LH-stimulated testosterone production by inhibiting, at least partially, 17 alpha-hydroxylase enzyme activities. Because FGF has been purified from testis extracts, this growth factor may have intratesticular paracrine or autocrine functions.

Rapid changes in the expression of inhibin alpha-, beta A-, and beta B-subunits in ovarian cell types during the rat estrous cycle

Distributions of inhibin alpha-, beta A-, and beta B-subunits in different ovarian compartments were studied in cycling female rats by in situ hybridization with complementary RNA probes and using immunohistochemical localization with antibodies selective for each inhibin subunit. Consistent with earlier studies showing inhibin production by granulosa cells of maturing follicles, we also detected mRNAs for inhibin alpha-, beta A-, and beta B-subunits in granulosa cells of these follicles. However, based on immunohistochemistry and in situ hybridization, we found that inhibin alpha- is not only expressed in granulosa cells of mature follicles but in follicles at all stages of maturation, including primary to tertiary follicles. A number of primordial follicles also contained alpha mRNA and immunodetectable alpha-subunit. Interestingly, theca interna and interstitial gland cells contained inhibin alpha mRNA and alpha-subunit. Low levels of inhibin alpha immunoreactivity as well as specific hybridization to the complementary inhibin alpha mRNA probe were observed in newly formed luteal tissue. beta-Subunits, on the other hand, were detected exclusively in granulosa cells of healthy tertiary follicles. The changes in expression of inhibin alpha-, beta A-, and beta B-subunits were more pronounced during the follicular phase of the cycle: inhibin alpha reached its highest level in granulosa cells, theca interna, and interstitial gland cells a few hours after the LH/FSH surge, while at the same time the beta-subunits decreased dramatically in granulosa cells of mature follicles. Immediately before ovulation (estrus 0200 h), the alpha-subunit sharply declined in preovulatory follicles and was present mainly in granulosa cells from nonovulatory follicles at various stages of maturation. At that time, the beta A- and beta B-subunits could not be detected in preovulatory follicles but were localized mainly in small tertiary follicles (less than 300 microns). Unlike for the alpha- and beta B-subunits, beta A mRNA and immunoreactivity was present in large tertiary follicles (approximately 600 microns) immediately before ovulation. The present findings support the hypothesis that a decrease in inhibin production could be responsible for the secondary FSH surge observed early on estrus. This could be initiated by a change in the ratios of activin-inhibin production by decreasing first, the levels of beta-subunits, second, the levels of alpha-subunit, and third, by a resurgence of activin A produced mainly by granulosa cells from large tertiary follicles.(ABSTRACT TRUNCATED AT 400 WORDS)

Cloning and characterization of a cDNA for rat tissue-type plasminogen activator

Two partly overlapping lambda gt11 cDNA clones coding for the 22S rat tissue-type plasminogen activator (t-PA) mRNA were isolated. The cDNA sequences cover 2445 nucleotides of the mRNA, including a 5' untranslated region of 31 nucleotides, an open reading frame of 1677 nucleotides, a 3' untranslated region of 737 nucleotides, and a poly(A) tail. The open reading frame codes for a 17-amino-acid signal peptide, a propeptide with 12 amino acids, and the mature protein with 530 amino acids. Rat t-PA has 81% and 92% amino acid sequence identity with the human and mouse counterparts and an equal distribution of conserved amino acids, suggesting that the proteins can fold into identical three-dimensional structures. The rat t-PA sequence contains two putative N-glycosylation sites at Asn-120 and Asn-452, while human t-PA has an additional glycosylation site at Asn-187. The site at Asn-187 is glycosylated in the human protein, revealing a different glycosylation pattern between the human and rat proteins.

Hormonal regulation of tissue-type plasminogen activator messenger ribonucleic acid levels in rat granulosa cells: mechanisms of induction by follicle-stimulating hormone and gonadotropin releasing hormone

FSH and GnRH both stimulate rat granulosa cells to produce tissue-type plasminogen activator (tPA). We have studied the molecular mechanisms involved in the action of these hormones by measuring tPA mRNA levels in primary cultures of rat granulosa cells. When granulosa cells were cultured in the presence of FSH or GnRH the level of tPA mRNA was increased 20- and 12-fold, respectively. The induction of tPA mRNA by FSH and GnRH was additive and the kinetics of induction differed. The effect of FSH could be mimicked by bromo-cAMP or forskolin, and was drastically enhanced by cotreatment with the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine. These findings are consistent with the notion that FSH mediates its effect through the protein kinase A pathway. GnRH is believed to augment phospholipid turnover in granulosa cells, leading to the activation of the protein kinase C pathway. Like GnRH, the protein kinase C activator phorbol myristate acetate also induced tPA mRNA in granulosa cells. In the presence of the protein synthesis inhibitor, cycloheximide, FSH-stimulated tPA message levels were enhanced by 30-fold, revealing superinduction of tPA mRNA levels by this pathway. In contrast the induction of tPA mRNA by GnRH was inhibited by cycloheximide indicating that the synthesis of an intermediate protein is required for the GnRH effect. Our data suggest that FSH and GnRH increase the tPA mRNA levels by two distinct pathways in cultured granulosa cells, providing a model system for studying the hormonal regulation of tPA gene expression.

Age-dependent changes in physiological action, content, and immunostaining of inhibin in male rats

We examined the role of endogenous inhibin in modulating FSH secretion in male rats during the infantile (days 10 to 21), juvenile (days 22 to 35), and pubertal (days 36 to 90) periods by 1) neutralization of endogenous inhibin using specific antibodies, 2) measurement of plasma and testicular levels of immunoreactive inhibin, and 3) immunohistochemical detection of testicular inhibin. In all studies, we used an antiserum against the first 26 N-terminal amino acids of the alpha-chain of porcine inhibin (anti-alpha-inhibin). Plasma immunoreactive inhibin levels were highest in young rats (8-15 days old), then decreased steadily with age. In addition, iv injection of the inhibin-alpha antiserum caused significant (P less than or equal to 0.01 or P less than or equal to 0.05) elevations in plasma FSH levels in male rats aged 10-24 days, whereas no significant (P greater than 0.05) changes occurred in older animals. In the testes, immunoreactive inhibin levels, expressed as femtomoles per mg wet weight, also declined with age. Inhibin immunostaining was most prominent in the Sertoli cells, with the greatest staining in the testes of 8 to 15-day-old rats. These results suggest that endogenous inhibin plays a physiological role in suppressing FSH secretion in infantile male rats, at an age when Sertoli cells contain the largest amount of this protein.

Maintenance of the ratio of bioactive to immunoreactive follicle-stimulating hormone in normal men during chronic luteinizing hormone-releasing hormone agonist administration

Chronic administration of LHRH agonist analogs to humans reduces gonadal function through pituitary desensitization. Serum immunoreactive gonadotropin levels are modestly reduced, whereas serum bioactive LH levels are drastically suppressed. The effects on bioactive FSH levels, however, are not known. In this study, serum bioactive FSH was measured using an in vitro granulosa cell aromatase bioassay in four normal men given a LHRH agonist, [D-Trp6,Pro9-NEt]LHRH (LHRHA; 500 micrograms/day for 16 weeks), by sc infusion and testosterone enanthate (TE; 100 mg, im every 2 weeks) and in five men given 500 micrograms/day LHRHA by daily sc injection for 20 weeks and TE (100 mg every 2 weeks) from weeks 10 through 20. During the first study, serum immunoreactive FSH levels (IR-FSH) decreased by 56.5 +/- 4.8% (+/- SEM), and serum bioactive FSH (Bio-FSH) level decreased by 57.6 +/- 6.4%. The ratio of Bio-FSH to IR-FSH did not change. During the second study, both serum IR-FSH and Bio-FSH levels followed a triphasic pattern, decreasing slightly but not significantly immediately after initiation of LHRHA administration, progressively increasing to a peak (P less than 0.5 vs, baseline) at week 10, and then, after addition of TE to this regimen, decreasing slightly again. The Bio-FSH to IR-FSH ratio, as in the first study, did not change. When serum obtained at week 10 during the second study, just before initiation of TE, was chromatographed on a Sephadex G-100 column, IR-LH eluted in two distinct peaks, while IR-FSH eluted as a single peak. These results demonstrate that in normal men chronic LHRHA administration alone for up to 10 weeks or LHRHA plus TE for up to 16 weeks does not alter the qualitative characteristics of secreted FSH, since there was no dissociation between serum IR- and Bio-FSH levels.

Gonadotropin-releasing hormone induces ovulation in hypophysectomized rats: studies on ovarian tissue-type plasminogen activator activity, messenger ribonucleic acid content, and cellular localization

GnRH and its agonists are known to induce ovulation in hypophysectomized rats by acting directly at the ovary. Because tissue-type plasminogen activator (tPA) has been implicated in the gonadotropin induction of ovulation, we examined the effect of an ovulatory dose of GnRH on ovarian tPA activity, mRNA content, and cellular localization. Hypophysectomized immature rats were injected sc with 20 IU PMSG and a single dose of a GnRH agonist (GnRHa; des-Gly10,DLeu6(N alpha Me)Leu7,Pro9NHEt-GnRH) 58 h later. At different times after treatment, ovaries were prepared for morphological analysis. Using a fibrin overlay method, tPA activities were measured in ovarian homogenates and cumulus-oocyte complexes, whereas granulosa cells were cultured for 24 h to estimate tPA secretion. Total ovarian RNA was prepared for hybridization analysis of tPA message levels, and tPA localization was studied by immunohistochemistry of ovarian sections. GnRHa induced ovulation in PMSG-primed hypophysectomized rats 14-16 h after injection in a dose-dependent manner, and the GnRHa action was blocked by concomitant treatment with a GnRH antagonist. GnRHa stimulated the induction of tPA, but not urokinase-type PA, activity in ovarian homogenates and granulosa cell-conditioned medium in a time-dependent manner, reaching a maximum before ovulation. tPA activity in cumulus-oocyte complexes was also increased before ovulation, but this increase was sustained. Hybridization analysis of steady state tPA mRNA levels was performed using a rat cRNA probe. Northern blot analysis of total ovarian RNA demonstrated that GnRHa stimulated tPA mRNA levels 12 h after treatment, with a subsequent decrease 24 h after treatment. Immunohistochemistry indicated substantial increases in tPA staining in granulosa cells and oocytes of preovulatory follicles before ovulation. Thus, GnRHa acts through specific receptors to increase ovarian tPA enzyme activity, mRNA content, as well as immunostaining in granulosa cells and oocytes. Like gonadotropins, GnRH may induce ovulation by directly stimulating tPA levels in the ovary.

The dependency of bioactive follicle-stimulating hormone secretion on gonadotropin-releasing hormone in hypogonadal and cycling women

An antagonist analog of GnRH, (Ac-delta 3-Pro1,p-F-D-Phe2,D-Trp3,6)GnRH (4F-antagonist), was administered to normal women and women with hypergonadotropic hypogonadism. Serum FSH levels were determined by both the granulosa cell aromatase bioassay and RIA. The constant infusion of 4F-antagonist (30 micrograms/kg.h) to the four hypogonadal women resulted in a more pronounced decline in bioactive FSH (62%) than in immunoreactive FSH levels (30%), and the FSH bioactive to immunoreactive ratio decreased significantly (P less than 0.05). Infusion of 4F-antagonist in normal women in the midfollicular phase revealed a similar pattern of suppression of bioactive (64%) and immunoreactive FSH (29%). When 4F-antagonist was administered sc at a dose of 80 micrograms/kg twice daily for 3 days to normal women in the midfollicular phase of their cycles, the bioactive FSH response was biphasic, with the maximal decrease on the second day, followed by return to basal levels on the third day. Correspondingly, there was a precipitous decline in serum estradiol (apparent demise of the dominant follicle), followed by a progressive rise in estradiol levels. Thus, in contrast to immunoreactive FSH levels, bioactive FSH more clearly reflects the biological action of FSH on the follicle in response to GnRH antagonist administration in women. The disparity in the quantitative decline between serum bioactive and immunoreactive FSH levels after presumed blockade of the GnRH receptor may reflect the microheterogeneity of the FSH molecule and suggests that alterations in the biological activity of secreted FSH may be GnRH dependent.

Inhibin: studies of stored and secreted forms by biosynthetic labeling and immunodetection in cultured rat granulosa cells

The biosynthesis of inhibin in rat granulosa cells was studied by biosynthetic labeling, immunoblotting, and immunocytochemical techniques. Granulosa cells from immature hypophysectomized estrogen-treated rats were cultured in the presence of [35S]cysteine. Both conditioned media and cell extracts were subjected to immunoprecipitation with an antibody directed against the N-terminal 26 amino acids of the alpha-chain of porcine inhibin (pI alpha 1-26), followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fluorography. Treatment with FSH (100 ng/ml) and delta 4-androstenedione (10(-7) M) increased the secretion of 35S-labeled inhibin immunoreactivity by 2.6-fold over that in control cultures treated with androstenedione alone. The radiolabeled inhibin had mol wt (Mr) values of 45,000 and 30,000. Upon reduction, the 45,000 Mr polypeptide remained (with increased apparent Mr of 49,000), but the 30,000 Mr species disappeared with the concomitant appearance of two bands with 18,000 and 11,000 Mr. Competition studies with pI alpha 1-26 confirmed that these polypeptides were all related to inhibin. Furthermore, immunoblotting with an antibody directed against the porcine inhibin beta-A chain (pI beta A81-113) indicated that the 11,000 Mr peptide was the inhibin beta-A chain. Extracts of cells treated with FSH contained only a high Mr alpha-related species (Mr, 41,000 nonreduced; 49,200 reduced). The inhibin alpha antibody was also used to immunocytochemically stain cultured granulosa cells. Cells that had been treated with FSH or the adenyl cyclase activator forskolin (3 x 10(-5) M), but not untreated cells, exhibited positive staining. These results indicate that granulosa cells synthesize and store inhibin alpha-chain precursor with 49,000 Mr. Although some of the high Mr alpha-form was secreted, the majority of the alpha-subunit was processed to the 18,000 Mr form and dimerized with the 11,000 Mr beta-chain to form the mature inhibin dimer immediately before secretion. The cultured granulosa cells may provide a model for future studies on the hormonal regulation of inhibin alpha- and beta-gene expression as well as subunit dimerization and secretion.

Serum bioactive and immunoreactive follicle-stimulating hormone in prostatic cancer patients during gonadotropin-releasing hormone agonist treatment and after orchidectomy

Serum bioactive and immunoreactive FSH levels were measured in five prostatic cancer patients during treatment for 6 months with the GnRH agonist analog buserelin (Hoechst; 600 micrograms, intranasally, 3 times per day) and for up to 12 weeks after subsequent orchidectomy. FSH bioactivity was measured using a sensitive specific in vitro granulosa cells aromatase bioassay. Before buserelin treatment, mean serum FSH bioactivity and immunoreactivity were 19.7 +/- 4.1 (+/- SE) IU/L (n = 5) and 13.7 +/- 3.8 IU/L, respectively, with a bioactivity to immunoactivity (B/I) ratio of 1.7 +/- 0.2. After the initiation of treatment with the GnRH agonist, FSH bio- and immunoactivities both transiently increased for 1-3 days. The increase in bioactivity was greater and prolonged, and the B/I ratio increased nearly 7-fold in 2 weeks. Serum FSH immunoreactivity declined to below the pretreatment level in 5 days and remained low for the rest of the treatment period. In contrast, serum FSH bioactivity did not decrease significantly below the pretreatment level during the 6-month treatment period, although the B/I ratio returned slowly toward the pretreatment value. After orchidectomy, both FSH activities increased dramatically, and the B/I ratio rose transiently from 1.5 to 7 in 2 weeks. Interestingly, serum FSH bioactivity and immunoreactivity decreased significantly (P less than 0.05) 1 day after orchidectomy in the buserelin-treated patients. In contrast, serum FSH immunoreactivity increased during the same period (P less than 0.05) in patients treated only by orchidectomy (FSH bioactivity was not measured). In conclusion, serum FSH bioactivity increases acutely more than FSH immunoreactivity after initiation of GnRH agonist treatment or orchidectomy. In the former case, serum FSH bioactivity subsequently returned to the pretreatment range. A clear decline during long term agonist treatment occurred only in serum FSH immunoreactivity, in contrast to the concomitant decline in serum LH bio- and immunoreactivities reported previously. The persistence of bioactive FSH may explain the inconsistent effects of GnRH agonist treatment on the suppression of spermatogenesis. The acute decrease in serum FSH after orchidectomy in the buserelin-treated men suggests that the testes may produce a factor that stimulates pituitary FSH secretion.

Naturally occurring antihormones: secretion of FSH antagonists by women treated with a GnRH analog

Follicle-stimulating hormone (FSH) is a glycoprotein essential for gonadal development and steroidogenesis. Recent studies suggest that deglycosylation of FSH results in the formation of antagonistic proteins that are capable of binding to gonadal receptors but that are devoid of bioactivity. Treatment of hypogonadal women with an antagonist of gonadotropin-releasing hormone substantially decreased serum FSH bioactivity with minimal changes in immunoreactivity. Chromatofocusing and size fractionation of the serum samples indicated the secretion of immunoreactive FSH isoforms that are devoid of bioactivity but that are capable of blocking FSH action in ovarian granulosa cells. These findings provide the first demonstration of naturally occurring circulating antihormones. These FSH antagonists may play an important role in the physiology and pathophysiology of the gonads.

Effect of transforming growth factor-beta on human chorionic gonadotropin induced testosterone production by cultured rat testicular cells

The potential role of transforming growth factor-beta (TGF-beta) as an intragonadal regulator in the testis was investigated by studying the effect of TGF-beta on testosterone (T) production by neonatal rat testis cells in primary cultures. After 3 days of preincubation in serum-free medium, testis cells were treated with hormones for 3 additional days. Human chorionic gonadotropin (hCG) treatment (0.3-30 ng/ml) of testis cells elicited a dose-dependent increase of T levels with maximum values greater than 9-fold over baseline. Although TGF-beta alone did not affect T levels, a dose-dependent inhibition of hCG-stimulated T production was observed when cells were cotreated with TGF-beta. Maximal inhibition was greater than 85%, and the IC50 value was 5 ng/ml (2 x 10(-10) M; n = 5 experiments). This inhibitory effect was evident 48 h after the initiation of treatment and could be reversed 1 day after the cessation of TGF-beta exposure of cells. TGF-beta also reduced forskolin and (Bu)2cAMP-induced T production (greater than 85% decrease), indicating that TGF-beta can inhibit steroidogenesis distal to the formation of cAMP. The conversion of exogenously added androgen precursors (progesterone (P) and 17 alpha-hydroxyprogesterone) to T by hCG-stimulated cells was suppressed by the addition of TGF-beta. In contrast, endogenous P accumulation did not change in cultures treated with TGF-beta. Because TGF-beta-like activity has been found in the testis, the observed inhibitory effect of TGF-beta suggests a potential intratesticular regulatory role of this growth factor.

Gonadotropin regulation of tissue-type and urokinase-type plasminogen activators in rat granulosa and theca-interstitial cells during the periovulatory period

Plasminogen activators (PAs) are believed to be involved in ovulation. Because both tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) are secreted by cultured rat granulosa cells, we have examined the activities of these proteins in ovarian homogenates as well as granulosa and theca-interstitial (TI) cells during gonadotropin-induced ovulation. Immature rats were injected with 20 IU pregnant mare serum gonadotropin (PMSG) to initiate follicle development, followed by treatment with 10 IU hCG 48 h later to induce ovulation. Ovarian proteins were separated by SDS-PAGE and PA activity determined by fibrin overlay. The activity of tPA, but not uPA, was stimulated following PMSG treatment in ovarian homogenates. Subsequent hCG injection further increased the tPA activity in a time-dependent manner, reaching a maximum (12 h after hCG treatment) immediately prior to ovulation and declined thereafter. Similar preovulatory increases in tPA activity were detected in isolated granulosa cells. Although both tPA and uPA activities were increased in TI cells after PMSG administration, no further increases were detected after hCG treatment. To estimate enzyme secretion, ovarian cells obtained at various preovulatory periods were incubated for 24 h in vitro. The ability of granulosa cells to secrete tPA, but not uPA, increased following in vivo PMSG and hCG treatment in a time-dependent manner, reaching a maximum immediately prior to ovulation. During the preovulatory period, an abrupt increase in tPA secretion by TI cells was also detected. Using immunohistochemical staining for tPA, it was found that ovarian sections from preovulatory rats at 12 h after hCG injection stained positively in granulosa, theca interna, and interstitial gland cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of the granulosa cell aromatase bioassay for measurement of bioactive follicle-stimulating hormone in urine and serum samples of diverse species

Ovarian steroids and growth factors are intragonadal modulators which augment a key endpoint of follicle-stimulating hormone (FSH) action in granulosa cells: the induction of aromatase activity. Studies of these paracrine hormones that enhance FSH-stimulated estrogen biosynthesis by cultured rat granulosa cells, have led to the development of a sensitive and specific in vitro bioassay for FSH. This newly developed granulosa cell aromatase bioassay (GAB) allows for the measurement of bioactive FSH levels in serum and urine of humans and animals with various physiological and pathological conditions. These studies have demonstrated that the GAB assay is useful in detecting possible changes in the molecular forms of FSH. The adaptation of this method for urine samples allows for the measurement of bio-FSH levels in situations where venipuncture is not practical or in species for which specific radioimmunoassays are not available.

Serum bioactive follicle-stimulating hormone in men with idiopathic azoospermia and oligospermia

Using an in vitro granulosa cell aromatase bioassay (GAB), serum bioactive FSH (bio-FSH) levels were measured in 20 fertile men and 74 men with idiopathic azoospermia or oligospermia. The serum bio-FSH levels measured by the GAB assay and the immunoreactive FSH (immuno-FSH) levels measured by RIA were positively correlated (r = 0.93). Compared to normal men, serum bio-FSH and immuno-FSH levels were elevated in patients with idiopathic azoospermia associated with severe germinal epithelium damage; the bioactive to immunoreactive ratio (B:I ratio) of FSH in these men [mean, 1.5 +/- 0.5 (+/- SD)] was significantly lower than that in fertile men (2.7 +/- 0.8). Similarly, in men with moderate and severe oligospermia, the B:I ratios of FSH were decreased (1.4 +/- 0.4 and 1.7 +/- 0.3, respectively). Although serum immuno-FSH levels correlated weakly with mean sperm concentrations in the normal and oligospermic men (r = -0.35), no relationship was found between serum bio-FSH and sperm concentrations. The B:I ratio of FSH correlated weakly with sperm concentration (r = 0.46). These findings suggest that the B:I ratio of FSH measured by the GAB assay decreases in patients with low sperm concentrations and germinal cell failure.

Regulation of tissue-type plasminogen activator activity and messenger RNA levels by gonadotropin-releasing hormone in cultured rat granulosa cells and cumulus-oocyte complexes

Gonadotropin-releasing hormone (GnRH) acts directly on the ovary to induce ovulation in hypophysectomized proestrous rats. Because plasminogen activators (PAs) are implicated in gonadotropin-induced ovulation, we have studied the effect of GnRH on ovarian PA synthesis. GnRH induced tissue-type PA (tPA) secretion by cultured rat granulosa cells, but inhibited the secretion of urokinase-type PA. These effects were blocked by co-treatment with a GnRH antagonist, suggesting that stereospecific GnRH receptors are involved. Follicle-stimulating hormone (FSH) also induced tPA in granulosa cells but with a different time course than GnRH; the combined effect of FSH and GnRH was additive. The GnRH effect was mimicked by the calcium- and phospholipid-dependent protein kinase C activator, phorbol myristate acetate. In isolated cumulus-oocyte complexes and cumulus cells, GnRH treatment also increased tPA activity. In contrast, treatment of denuded oocytes with GnRH did not increase enzyme activity. After GnRH stimulation of the cumulus-oocyte complexes, tPA content in the denuded oocyte was elevated, suggesting that the cumulus cells mediate the action of GnRH to increase the oocyte enzyme levels. Hybridization experiments using a labeled rat tPA-specific DNA probe showed that both FSH and GnRH increased the level of tPA mRNA in cultured granulosa cells; the stimulatory effect of GnRH was blocked by the GnRH antagonist. Our results indicate that GnRH treatment increases tPA secretion by cultured granulosa cells and cumulus-oocyte complexes. The stimulation of enzyme activity in the granulosa cells is accompanied by increases in tPA mRNA levels.

Rat inhibin: molecular cloning of alpha- and beta-subunit complementary deoxyribonucleic acids and expression in the ovary

Inhibin is a gonadal protein hormone that suppresses the secretion of FSH from pituitary gonadotrophs. It has previously been characterized as a heterodimer of two dissimilar subunits (alpha, 18 kilodaltons and beta, 14 kilodaltons) the smaller of which exists in two forms (beta A and beta B) and can form dimers that stimulate the secretion of FSH. In the present work, cDNA clones encoding the inhibin alpha- and beta A-subunits have been isolated from rat ovary and characterized. The alpha-inhibin cDNA predicts a precursor protein of 366 amino acids containing the 133 amino acid mature alpha-subunit at its COOH-terminus. The beta A-inhibin cDNA predicts a precursor protein of 424 amino acids containing the 116 amino acid beta A-subunit at its COOH-terminus. Analysis of rat ovarian RNA indicates that alpha-inhibin mRNA levels are stimulated by PMSG treatment in vivo. In cultured granulosa cells, FSH also stimulates alpha-inhibin mRNA, and the FSH effect is suppressed by cotreatment with GnRH. Hybridization in situ to rat ovarian tissue demonstrates that both the alpha-inhibin and beta A-inhibin mRNAs are specifically expressed in granulosa cells of the developing follicles.

Insulin-like growth factor-I augments gonadotropin-stimulated androgen biosynthesis by cultured rat testicular cells

In addition to the well-known growth stimulating effects of insulin-like growth factors (IGFs), recent studies suggest that these peptides may also modulate the differentiated functions of endocrine cells. Thus, in the present studies, we have investigated the actions of IGFs on androgen biosynthesis by cultured testicular cells. Treatment of cells obtained from adult hypophysectomized rats with LH (1 ng/ml) stimulated testosterone production 60-fold over basal levels. In contrast, treatment with either synthetic human IGF-I or IGF-II failed to stimulate androgen production. However, concomitant treatment of the LH-containing cultures with increasing doses of IGF-I (10-500 ng/ml) augmented testosterone production up to 70% over that seen with LH alone (ED50 = 67 ng/ml). Similar effects were obtained with IGF-II but this peptide was about 10-fold less potent than IGF-I. In addition, these peptides also stimulated the accumulation of pregnenolone and progesterone in the culture medium. Additional studies demonstrated specific binding of [125I]iodo-IGF-I to testicular cells. This binding was competed by IGF-related peptides with the potency order IGF-II = IGF-I greater than insulin whereas unrelated peptides did not compete. The cellular localization of these receptors was examined in testicular cells separated on a metrizamide density gradient. IGF-I receptors were evenly distributed between two cell peaks containing subpopulations of Leydig cells whereas much less binding was found in other testicular cell types. Coupled with recent findings indicating testicular production of IGF-I, the present results suggest that this peptide may act as a positive intratesticular modulator of Leydig cell differentiation.

Heterodimers and homodimers of inhibin subunits have different paracrine action in the modulation of luteinizing hormone-stimulated androgen biosynthesis

Inhibin, a gonadal hormone capable of preferential suppression of pituitary follicle-stimulating hormone (FSH) secretion, has recently been purified. The major form of this protein is an alpha beta heterodimer encoded by two separate genes. In contrast to the FSH-suppressing action of the alpha beta heterodimer, the beta beta homodimer stimulates FSH secretion. Luteinizing hormone (LH)-secreting pituitary cells and gonadal androgen-producing cells have long been shown to form a closed-loop feedback axis. Based on recent studies demonstrating the FSH stimulation of inhibin biosynthesis by ovarian granulosa and testis Sertoli cells, an additional closed-loop feedback axis exists between pituitary FSH- and gonadal inhibin-producing cells. Because uncharacterized Sertoli cell factors have been suggested to either stimulate or inhibit androgen production by testicular Leydig cells, we have tested the intragonadal paracrine actions of heterodimers and homodimers of inhibin subunits. In primary cultures of testis cells, the alpha beta heterodimer of inhibin enhances Leydig cell androgen biosynthesis stimulated by LH, whereas the beta beta homodimer suppresses androgen production. Furthermore, similar modulatory actions of inhibin-related proteins were found in cultured ovarian theca-interstitial cells and theca explants treated with LH. In contrast, treatment with the inhibin-related proteins alone did not affect gonadal steroidogenesis. Our data indicate that the inhibin-related gene products synthesized by Sertoli and granulosa cells may form heterodimers or homodimers to serve as intragonadal paracrine signals in the modulation of LH-stimulated androgen biosynthesis and allow cross-communication between the two feedback loops.

Serum bioactive and immunoreactive follicle-stimulating hormone levels and the response to clomiphene in healthy young and elderly men

Testicular function declines with normal aging, while serum immunoreactive LH and FSH levels increase. Since there are reports of an age-related decrease in the ratio of bioactivity to immunoreactivity (B/I ratio) for LH, we used a newly available bioassay for FSH to assess age-associated changes in the bioactivity and B/I ratio of FSH in man. Thirty-nine healthy men (23 young and 16 elderly) had single blood samples drawn. In addition, a subset of these men (12 young and 13 elderly) underwent frequent blood sampling for 24 h, both before and after 7 days of clomiphene citrate (CC) administration. Hourly blood samples from the 24-h sampling were pooled, and these, along with the single samples, were assayed for FSH by an in vitro bioassay system, using estrogen production by immature rat granulosa cells as the end point, and by RIA. Baseline single sample mean FSH, as measured by bioassay, was similar in young and elderly men [386 +/- 98 (+/- SEM) and 342 +/- 77 ng/mL, respectively]. Baseline mean FSH, measured by RIA, was significantly higher (P less than 0.001) in elderly men (234 +/- 31 ng/mL) than in young men (122 +/- 12 ng/mL). The baseline FSH B/I ratio based on single sampling was significantly lower (P less than 0.01) in elderly men (1.4 +/- 0.2) than in young men (2.7 +/- 0.3). In the men given CC and sampled for 24 h, mean bioactive FSH levels increased significantly in both the young (1180 +/- 282 ng/mL) and the elderly (992 +/- 227 ng/mL; P less than 0.01 for both values compared to baseline). Mean FSH by RIA also increased to similar levels in these young (217 +/- 34 ng/mL) and elderly (258 +/- 45 ng/mL) men. The FSH B/I ratio was 4.8 +/- 0.8 in young and 4.7 +/- 1.1 in elderly men after CC administration. We conclude that serum bioactive FSH levels are similar in elderly and young men, suggesting that the age-related decline in testicular function in man cannot be explained by a chronic deficiency in FSH stimulation; elderly men have a lower serum FSH B/I ratio than young men, which may reflect changes in the circulating form of FSH with aging; and administration of CC to young and elderly men increases both bioactive and immunoreactive serum FSH, implying preserved hypothalamic-pituitary responsiveness in the elderly.

Plasminogen activator activity in cumulus-oocyte complexes of gonadotropin-treated rats during the periovulatory period

Two types of plasminogen activator (tissue-type, tPA; urokinase-type, uPA) have been demonstrated in ovarian granulosa cells, but only tPA activity was found in denuded oocytes. Immature rats were treated subcutaneously with 20 IU pregnant mare's serum gonadotropin (PMSG) to stimulate follicle maturation, followed 2 days later by an injection of 10 IU human chorionic gonadotropin (hCG) to induce ovulation. Cellular plasminogen activator activities were determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis followed by a fibrin-overlay technique. Cumulus-oocyte complexes from rats before and after PMSG treatment contained low amounts of tPA, but not uPA, activity. After hCG treatment, tPA activity showed a time-dependent increase, reaching a maximum at 24 h after injection. At 12 and 24 h after hCG treatment, uPA activity was also detected. The appearance of high molecular weight lysis zones further suggested the formation of plasminogen activator-inhibitor complexes. Morphological analysis indicated that the increases in oocyte tPA activity were correlated with the extent of cumulus cell expansion and dispersion. In denuded oocytes, tPA activity also progressively increased during the periovulatory period to a maximum at 24 h after hCG treatment. In contrast, neither uPA activity nor activator-inhibitor complex was detected. Secretion of the proteases was measured in the conditioned media of cumulus-oocyte complexes cultured for 24 h in vitro. Substantial increases in tPA release were found in complexes obtained at 8 and 12 h after hCG injection, with lower secretion from complexes obtained at 24 h after hCG treatment.(ABSTRACT TRUNCATED AT 250 WORDS)