LH Receptor Content Research Articles

The effect of peritoneal macrophage-derived factor(s) on ovarian progesterone secretion and LH receptors: the role of calcium.

Macrophages and their secretory products, cytokines, play an integral role in many reproductive processes. In this study we examined the effect of conditioned media from cultured human peritoneal macrophages on progesterone production by granulosa cells and the role of calcium in this process. Macrophages were pretreated with various concentrations of a calcium channel blocker (verapamil) or a calcium ionophore (A23187). Macrophage-conditioned media (MCM) or cell-free media that contained calcium channel modifiers were added at three dose levels to cultured porcine granulosa cells. Progesterone production and LH receptor content were determined. Macrophage-conditioned media alone elevated basal progesterone production, but significantly attenuated granulosa cell LH receptor content. These effects were neither potentiated nor suppressed by pretreating macrophages with verapamil. However, production of the LH receptor lowering factor(s) appeared to be suppressed by calcium ionophore. We conclude that (1) one or more factors produced by macrophages have a net stimulatory effect on basal progesterone production and these factor(s) may not be calcium-dependent and (2) macrophage-derived secretory products reduce granulosa cell LH receptor content. The production of these factor(s) may be calcium-dependent.

Structural changes in rat Leydig cells posthypophysectomy: a morphometric and endocrine study.

Short and long term responses of the rat Leydig cell were studied posthypophysectomy, at times when germ cell degeneration was first prominent (6 days) and after long term regression of the testis (28 days). In the short term, virtually all structural parameters relating to the volume and surface area of the Leydig cell and its subcellular organelles were significantly lowered compared with those in control animals. Exceptions were the volumes of the nucleolus, heterochromatin, and lysosomes and the surface areas of the nucleus. Structural decreases were generally on the order of 2- to 5-fold in the 6-day period. A statistical analysis of the percent decreases in the short term was performed to determine whether any particular structural features were more sensitive to hypophysectomy than any others. In most instances, no particular organelles were decreased compared to others. However, lipid, although not commonly seen in rat Leydig cells, showed significantly greater percent decreases compared with several other organelles, indicating that the small amount of lipid present is rapidly lost (used) in the short term. After long term hypophysectomy, all structural parameters of the Leydig cell were significantly lowered compared with those in pituitary-intact animals. Only a few parameters (mitochondrial volume, cell surface area, and the surface areas of inner and outer mitochondrial membranes and smooth endoplasmic reticulum) showed more significant decreases in the long term compared with the short term hypophysectomized animals. Most organelle volumes and surface areas correlated positively and significantly with serum and tissue testosterone levels; the exceptions were the volumes of the nucleolus, heterochromatin, lipid, and lysosomes. Compared with the pituitary-intact animal, the content of LH receptors expressed per testis and per Leydig cell was significantly lower in both hypophysectomized groups; however, the number of receptors per given area of individual Leydig cell plasma membrane remained unchanged. Overall, data show that the Leydig cell manifests marked structural changes during early spermatogenic dysfunction.

Dose-dependent effects of human prolactin on the immature hypophysectomized rat testis.

We have studied dose-dependent effects of highly purified human PRL (39 IU/mg) on the testis of immature (22-day-old) hypophysectomized rats daily supplemented for 7 days with 2, 10, or 30 micrograms hormone. Dose-dependent stimulation was observed for all parameters: testis weight (1.6- and 2-fold above control for 10 and 30 micrograms PRL), basal and hCG-stimulated testosterone (14- and 21-fold), intratesticular testosterone (7- and 21-fold) and estradiol (1.2- and 1.5-fold), LH receptor concentration (1.8- and 2.5-fold), in vitro pregnenolone production by cholesterol side-chain cleavage enzyme (3-, 5- and 7-fold), and aromatase activity (2.1- and 2.4-fold). The number of Leydig cells exhibiting immunoreactivity toward anti-P450scc, anti-P450(17 alpha), and anti-3 beta-hydroxysteroid dehydrogenase antibodies also underwent a dose-dependent increase (under conditions revealing many immunopositive cells in hypox control animals). The respective increases were 8- to 14-fold for anti-P450scc and P450(17 alpha) and 1.5- to 2-fold for anti-3 beta-hydroxysteroid dehydrogenase. The number of germ cells and the percentage of tubular sections containing late pachytene spermatocytes as most advanced stages of spermatogenesis were subject to similar dose-dependent effects. These results suggest that during puberty PRL stimulates testicular function by promoting multiplication and differentiation of Leydig cells (acting at various steps of steroidogenesis and on tissue responsiveness to LH) and germ cells.

Combination of a GnRH agonist with an antiandrogen or bromocriptine in the treatment of prostatic cancer; slight potentiation of antigonadal effects

The effect of combined treatment with a GnRH agonist (buserelin depot, BUS, 6.6 mg every 2 months) with an antiandrogen (cyproterone acetate, CPA, 300 mg day-1) or a prolactin-suppressing agent (bromocriptine, BR, 20 mg day-1) on pituitary-testicular function were studied in patients with advanced prostatic carcinoma. The patients (n = 5-6 per group) were treated in this fashion for 6 months and thereafter orchidectomized. Serum testosterone and gonadotrophin responses were followed during treatment, and histology and certain endocrine parameters were studied using testicular tissue obtained at orchidectomy. Serum LH was suppressed in all treatment groups from mean levels of 4-6 IU l-1 to less than 0.1 IU l-1, whilst serum FSH levels decreased in all groups during the first month of therapy from 4.5-7 to 1-2 IU l-1, but recovered thereafter. Only minor increases in serum gonadotrophin levels were evident 3 months after castration. No differences in gonadotrophin responses were seen between the different treatment groups. Serum levels of testosterone were suppressed from 15-20 nmol l-1 to the castrate range (approximately 1 nmol l-1), in each of the treatment groups. Testicular weight decreased significantly more (P less than 0.05) in the BUS + CPA group, compared to the other treatments. No differences were found in the testicular concentration of testosterone, or LH and FSH receptors between the three treatment groups. On histological examination, spermatogenesis was found to be impaired severely in all groups, with the lowest Johnsen score in the BUS + BR group (2.16 +/- 0.13, vs. 2.73 +/- 0.25 with BUS alone, P less than 0.05). Seminiferous tubular diameters were reduced similarly in all treatment groups. In conclusion, the combination of CPA or BR with BUS in the treatment of prostatic carcinoma does not potentiate the suppression of gonadotrophin or testosterone secretion, evidently because the GnRH agonist exerts a maximal suppressing effect. However, other antigonadal effects were enhanced slightly, including suppressed testicular weights by CPA and further suppression of spermatogenesis by BR.

Stimulatory Effects of Recombinant Follicle-Stimulating Hormone on Leydig Cell Function and Spermatogenesis in Immature Hypophysectomized Rats*

Although earlier reports suggest a stimulatory effect of FSH on Leydig cell function, controversy exists due to unavailability of FSH preparations free of contaminating LH. Recent availability of recombinant human FSH preparations made it possible to reinvestigate this question. Immature male rats were hypophysectomized (21-22 days old at surgery) and implanted with osmotic minipumps releasing 8 IU recombinant FSH or 18 IU purified human pituitary FSH (hpFSH)/day, whereas control animals received vehicle alone. After 7 days of treatment, testicular weight increased in the recombinant FSH and hpFSH-treated animals to values 2.3- and 2.5-fold those of controls, respectively. Analyses of the steroidogenic capacity of Leydig cells in testes of rats treated with recombinant FSH or hpFSH also revealed 2.9- and 3.8-fold androgen production in vitro compared to controls. In these rats recombinant FSH and hpFSH increased the LH receptor number in testicular homogenate by 50% and 70%, respectively. The increase in LH receptor number was associated with increases in the LH receptor mRNA levels. In hypophysectomized control rats, small seminiferous tubules contained spermatogonia and zygotene/early pachytene spermatocytes. In contrast, treatment with either FSH preparation enhanced the progression of meiosis, as evidenced by large number of pachytene spermatocytes and appearance of round spermatids. The present results show that LH-free recombinant FSH, like purified pituitary FSH, is capable of increasing the LH receptor content and steroidogenic responsiveness of Leydig cells through paracrine mechanisms together with a stimulatory effect on spermatogenesis. These observations suggest that prepubertal elevation of FSH secretion may be important for increasing Leydig cell steroidogenic capacity and spermatogenic progression.

Regulation of Luteinizing Hormone Receptor Messenger Ribonucleic Acid Levels by Gonadotropins, Growth Factors, and Gonadotropin-Releasing Hormone in Cultured Rat Granulosa Cells*

The induction of LH receptors in granulosa cells is prerequisite for ovarian follicles to ovulate and form corpora lutea. Earlier studies have demonstrated the modulatory role of gonadotropins, growth factors, and GnRH on ovarian LH receptor content. We have now analyzed the influences of gonadotropins (FSH, LH, and PRL), several growth factors, and GnRH on LH receptor mRNA levels in cultured granulosa cells. Cells were obtained from immature estrogen-treated rats and cultured in medium containing FSH with or without growth factors or GnRH for 48 h. Some cells were also treated with FSH for 48 h, followed by treatment with FSH, LH, or PRL for another 2 days. Cellular total RNA was extracted, and blot hybridization with 32P-labeled LH receptor cRNA or 28S ribosomal RNA cDNA probes was performed. Treatment of granulosa cells with FSH increased the levels of five species of LH receptor mRNAs in a dose- and time-dependent manner. In FSH-primed cells, LH receptor mRNA levels were maintained by FSH, LH, and PRL. In contrast, treatment of cells with basic fibroblast growth factor or epidermal growth factor suppressed FSH induction of LH receptor mRNA in a dose-dependent manner, whereas treatment with insulin-like growth factor-I had no effect. In addition, GnRH suppressed FSH-stimulated LH receptor mRNA levels in a dose-dependent manner; the effects of GnRH could be counteracted by coincubation with a GnRH antagonist, suggesting mediation by specific GnRH-binding sites. These studies demonstrated that the observed stimulatory effects of gonadotropins (FSH, LH, and PRL) and the inhibitory effects of growth factors (epidermal growth factor and basic fibroblast growth factor) and GnRH on LH receptor content are correlated to their regulation of LH receptor mRNA levels. The granulosa cell culture system should provide a useful model for studying LH receptor gene regulation.

Impact of season on seminal characteristics and endocrine status of adult free-ranging African buffalo (Syncerus caffer)

Pituitary, gonadal and adrenal activity were compared in free-living, adult African buffalo bulls during the breeding and nonbreeding seasons. Frequent blood samples were collected for 2 h from anaesthetized bulls treated intravenously with saline, gonadotrophin-releasing hormone (GnRH, 200 micrograms), human chorionic gonadotrophin (hCG, 10,000 i.u.) or adrenocorticotrophic hormone (ACTH, 1.5 mg). Electroejaculates also were collected from anaesthetized bulls during the breeding and nonbreeding seasons. Pretreatment testosterone concentrations among bulls varied more during the breeding (0.17-23.0 ng/ml) than the nonbreeding (0.15-2.21 ng/ml) season. The variation within the breeding season was attributed to 8 of 25 bulls producing higher (P less than 0.05) serum testosterone (High-T; 16.28 +/- 2.03 ng/ml) and testicular LH receptor (1.53 +/- 0.22 fmol/mg testis) concentrations compared with their seasonal counterparts (Low-T; 0.95 +/- 0.26 ng/ml; 0.38 +/- 0.04 fmol/mg) or with all bulls during the nonbreeding season (0.90 +/- 0.27 ng/ml; 0.31 +/- 0.04 fmol/mg). The magnitude of GnRH- and hCG-induced increases in serum testosterone was similar (P greater than 0.05) between Low-T bulls and bulls during the nonbreeding season. In the High-T animals treated with GnRH or hCG, serum testosterone did not increase, suggesting that secretion was already maximal. Peak serum LH concentrations after GnRH were greater (P less than 0.05) in bulls during the nonbreeding than the breeding season; FSH responses were similar (P greater than 0.05). ACTH treatment did not increase serum cortisol concentrations above the 2-fold increase measured in bulls treated with saline, hCG and GnRH (P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental changes in pituitary-gonadal function in free-ranging lions (Panthera leo leo) of the Serengeti Plains and Ngorongoro Crater

Pituitary-gonadal function was examined in male lions free-ranging in the Serengeti Plains or geographically isolated in the Ngorongoro Crater of Tanzania. Lions were classified by age as adult (6.1-9.8 years), young adult (3.3-4.5 years) or prepubertal (1.4-1.6 years, Serengeti Plains only). Each animal was anaesthetized and then bled at 5-min intervals for 100 min before and 140 min after i.v. administration of saline or GnRH (1 micrograms/kg body weight). Basal serum LH and FSH concentrations were similar (P greater than 0.05) among age classes and between locations. In Serengeti Plains lions, net LH peak concentrations after GnRH were approximately 35% greater (P less than 0.05) in prepubertal than in either adult or young adult animals. GnRH-stimulated LH release was similar (P greater than 0.05) between adult and young adult lions, and these responses were similar (P greater than 0.05) to those measured in Ngorongoro Crater lions. Basal and GnRH-stimulated testosterone secretion was higher (P less than 0.05) in adult than in young adult lions and lowest (P less than 0.05) in prepubertal lions. Age-class differences in testosterone production were related directly to the concentrations of LH receptors in the testis (P less than 0.05). Basal and GnRH-stimulated testosterone secretion and gonadotrophin receptor concentrations within age classes were similar (P greater than 0.05) between lions of the Serengeti Plains and Ngorongoro Crater. Lower motility and higher percentages of structurally abnormal spermatozoa were observed in electroejaculates of young adult compared to adult Serengeti Plains males (P less than 0.05) and were associated with decreased steroidogenic activity. In contrast, there were no age-related differences in ejaculate characteristics of Ngorongoro Crater lions. Seminal quality in the Crater population was poor in adult and young adult animals and was unrelated to alterations in pituitary or testicular function. In summary, only seminal quality in adult male lions was affected by location, whereas age significantly affected both basal and GnRH-stimulated testosterone secretion and seminal quality (Serengeti Plains only) in sexually mature males. The striking seminal/endocrine differences among pride (breeding) males of different ages raises questions about the impact of age on individual reproductive performance in this species.

GONADOTROPIN-INDUCED UP- AND DOWN-REGULATION OF RAT OVARIAN LH RECEPTOR MESSAGE LEVELS DURING FOLLICULAR GROWTH, OVULATION AND LUTEINIZATION

Induction of follicular growth by PMSG is associated with increased ovarian LH receptor content, whereas the preovulatory surge of LH decreases LH binding sites, followed by a secondary increase in receptor numbers coincident with corpora lutea formation. Based on the recently reported LH receptor cDNA sequence, we have performed a reverse transcription-polymerase chain reaction to obtain LH receptor cDNA clones and generated a 32P-labeled cRNA probe to examine the dynamic changes in ovarian LH receptor mRNA levels during gonadotropin induction of follicular growth, ovulation and luteinization. Northern blot analysis of ovary RNA revealed hybridization signals of about 7.0, 4.2, 2.5 and 1.8 kb, with no hybridization to nongonadal tissues. PMSG increased the intensity of all four LH receptor messages at 24 h, preceding an increase in LH receptor number, with peak LH receptor mRNA and receptor content observed at 52 h. Treatment with hCG resulted in decreased LH receptor binding and mRNA levels by 6 h after injection, with maximal inhibition (greater than 85%) of message at 12 to 24 h after hCG treatment. Subsequently, LH receptor message levels increased again at 3 days after hCG, concomitant with increased [125I]hCG binding. A further increase in LH receptor content, but not message levels, was observed 5 days after hCG. These results demonstrate that the induction of LH receptors by PMSG is preceded by increased LH receptor mRNA levels. Furthermore, ligand-induced down-regulation of the LH receptor following an ovulatory dose of hCG is associated with decreased LH receptor message content, followed by increases in LH receptor message levels and binding sites during subsequent luteinization. Thus, the up- and down-regulation of ovarian LH receptors during follicle growth, ovulation and luteinization is probably due, at least in part, to changes in receptor message modulation.

Continuous and Pulsatile Infusions of Luteinizing Hormone Have Identical Effects on Steroidogenic Capacity and Sensitivity of Leydig Cells in Rats Passively Immunized against Gonadotropin-Releasing Hormone*

Adult male rats were passively immunized against GnRH and given iv infusions of saline or 60 or 300 ng NIDDK ovine LH-24/100 g BW.24 h in continuous regimens of 2.5 or 12.5 ng/100 g BW.h and pulsatile regimens of 1-min pulses of 5 or 25 ng/100 g BW every 2 h. Control animals were treated with nonimmune serum and saline. After 10 days of in vivo treatment, Leydig cells were purified and incubated in vitro with 1) increasing concentrations of hCG (0-50 mIU/ml) in the presence or absence of methylisobutylxanthine, 2) a maximally stimulatory concentration of 8-bromo-cAMP (8-Br-cAMP; 1 mM), and 3) a saturating concentration of 25-hydroxycholesterol (10 microM). LH receptor concentrations were quantified by [125I]hCG binding assay. Maximum testosterone production in the presence of hCG, 8-Br-cAMP, or 25-hydroxycholesterol was reduced by more than 90% in Leydig cells from anti-GnRH serum-treated rats (compared to that in cells from control rats), and this reduction in steroidogenic capacity was prevented in a dose-dependent manner by concurrent infusion of LH in either the continuous or pulsatile regimens. These results confirm that the trophic actions of LH on Leydig cells in vivo 1) do not depend on pulsatile secretion of the hormone, and 2) include induction/maintenance of one or more of the enzymes catalyzing the conversion of cholesterol to testosterone. Trophic actions on constituents or processes before cholesterol side-chain cleavage were not apparent; in vivo treatments had no obvious differential effects on hCG-stimulated, 8-Br-cAMP-stimulated, or 25-hydroxycholesterol-supported testosterone production. Sensitivity to hCG was increased (EC50 for stimulation of testosterone production was decreased) by passive immunization against GnRH, and this effect was prevented in a dose-dependent manner by concurrent infusion of LH in either the continuous or pulsatile regimens. Thus, intermittent exposure to low concentrations of LH in vivo desensitizes Leydig cells as effectively as continuous exposure. Neither specific binding of [125I]hCG nor the effect of methylisobutylxanthine on sensitivity to hCG in vitro differed among treatment groups. Therefore, both the trophic and desensitizing actions of LH appear to occur by mechanisms that are independent of changes in available LH receptor concentration and phosphodiesterase activity.

Hormonal basis of variation in oestrous cyclicity in selected strains of mice

Reproductive hormone secretion and ovarian LH receptor content were studied during the oestrous cycle of mice that differed in fertility after genetic selection. Strain variation in the secretory pattern of progesterone was observed along with differences in the timing and magnitude of prolactin release. Scatchard analysis showed similar affinities of the LH receptor for hCG in strains with increased or decreased reproductive performance, with a single order of binding sites during both pro-oestrus and dioestrus. The number of unoccupied LH receptors during pro-oestrus was greatest in mice with increased reproductive performance. These results provide evidence that trait selection can change gonadotrophin receptor concentration and the dynamics of hormone secretion during the oestrous cycle of the mouse.

Luteinizing hormone in nutrient-restricted ovariectomized ewes2

This study was designed to evaluate profiles of serum concentrations of LH, pituitary content of LH and GnRH receptors, and hypothalamic content of GnRH in undernourished, ovariectomized ewes. In earlier studies, pulsatile secretion of LH diminished as duration of undernutrition progressed in prepubertal or adult ovariectomized ewes. Ewes having similar body condition scores (CS) of 5 to 9 (1 = extremely thin, 5 = moderate, 9 = obese) were fed maintenance or low-energy diets (100% and 60% of NRC requirements, respectively). Blood samples for analysis of LH were collected at 15-min intervals for 4 h at initiation of the project and immediately prior to slaughter. Serum concentrations of LH did not differ (P greater than .05) among groups at the initial sampling period. At slaughter, ewes with CS less than or equal to 2 (n = 7) had lost 26.8 kg (42% of initial weight). Ewes with CS greater than or equal to 3 (n = 12) had lost an average of 13.7 kg (18% of initial weight). Concentrations of LH in ewes with final CS greater than or equal to 3 was similar (P greater than .05) to that observed during the initial sampling period. However, release of LH was reduced (P less than .01) in ewes with CS less than or equal to 2 compared with ewes with CS greater than or equal to 3 (2.6 vs 9.5 and 3.2 vs 10.5 ng/ml for basal and mean concentrations, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Structure/function relationships in active and inactive hamster Leydig cells: a correlative morphometric and endocrine study.

Spermatogenesis can be turned on or off in the seasonally breeding golden (Syrian) hamster in a laboratory setting by exposure of animals to different photoperiod regimens. The present study provides the first detailed quantitative analysis of the subcellular features of hamster Leydig cells during active and inactive phases of spermatogenesis and correlates these features with the endocrine activity of the same animals. Conventional stereological principles and accepted morphometric techniques were used to determine changes in a variety of subcellular constituents of Leydig cells at the extreme phases of gonadal activity produced by maintaining adult hamsters in a long photoperiod (16 h of light, 8 h of darkness) or by exposing them to a short photoperiod (6 h of light, 18 h of darkness) for 12-13 weeks. Compared with Leydig cells from gonadally active animals, Leydig cells obtained from the regressed testis showed a significant reduction in the absolute volume of nearly all of its organelles, including nucleolus (77.0%), mitochondria (50.0%), total endoplasmic reticulum (ER) (86.4%; cisternal ER, 87.0%; tubular ER, 85.5%), lipid (84.2%), peroxisomes (82.5%), multi-vesicular bodies (71.9%), filament-rich area (95.5%), and Golgi complex (69.4%). There was also a significant reduction in organelle surface area, namely outer (76.5%) and inner (72.7%) mitochondrial membrane, total ER (85.0%), cisternal (85.3%) and tubular (84.4%) forms of ER, and Golgi complex (70.0%). The surface areas of the plasma membrane and nuclear membrane were also decreased by 58.3% and 33.7%, respectively. These results demonstrate that the short photoperiod-induced cellular inactivity of Leydig cells is associated with an overall diminution in the volume and surface area of all major organelles, not only those specifically associated with steroid biosynthesis. Virtually every structural parameter of the Leydig cell was significantly and positively correlated with plasma LH levels and with both plasma and testicular concentrations of testosterone. The total content of LH receptors per testis and per Leydig cell was reduced, but the concentration of receptors per unit area of the Leydig cell surface remained unchanged. Correlation of changes in hormonal status with alterations of all Leydig cell organelles suggests a general shut-down of cellular activity in the gonadally regressed animals, rather than a specific effect of pituitary hormones on selected cellular constituents.

Tumor necrosis factor -α inhibits follicle-stimulating hormone-induced differentiation in cultured rat granulosa cells

We have investigated the effects of TNF-alpha on FSH-induced LH receptor expression, cAMP and progesterone production in cultured rat granulosa cells. TNF-alpha (0.5-100 ng/ml) inhibits the stimulating action of FSH on LH receptor formation in a dose-dependent manner with an IC50 of 1 ng/ml and an almost complete suppression of LH receptor induction for 50-100 ng/ml TNF-alpha. The inhibitory effect of TNF-alpha is not due to variations in cell number or viability but rather to a reduction of the LH receptor content per cell with no change in binding affinity (KD = 0.8 x 10(-10)M). TNF-alpha also inhibits the FSH-induced cAMP production but at a lower extent, with a maximum reduction of 60% for 100 ng/ml TNF-alpha. Moreover, TNF-alpha impairs the LH receptor formation induced by forskolin, cholera toxin or 8-Bromo-cAMP, indicating that the cytokine also acts at a step distal to FSH receptor and to cAMP formation. Finally, TNF-alpha decreases dramatically the progesterone synthesis that is stimulated by FSH, with a reduction to undetectable levels on and after 10 ng/ml TNF-alpha. These results suggest that TNF-alpha may drastically reduce the capacity of granulosa cells to differentiate upon FSH stimulation and to respond to LH during the physiological ovarian follicular maturation. Such anti-gonadotropic action of TNF-alpha on granulosa cell differentiation may be also relevant to the alteration of ovarian function during physiopathological processes like inflammatory or infection diseases.

Prepubertal treatment of rats with clomiphene citrate affects postpubertal testicular development

A previous study showed that clomiphene citrate (clomiphene) reduced serum and pituitary gonadotropins and impaired testis growth and steroidogenesis in 10-day-old rats treated for up to two weeks. The present study was conducted to assess the effect of prepubertal clomiphene treatment on postpubertal pituitary-testicular function. Rats were implanted with pellets that released 0, 0.05, 0.5 or 5.0 mg clomiphene.kg-1.day-1 between 10-31 days of age and were killed at 90 days of age. Testis and prostate weights in treated rats were reduced (P less than 0.05), whereas serum LH, FSH and testosterone, and pituitary gonadotropin and GnRH receptor concentrations had recovered to levels observed in control rats. Testicular FSH receptor concentrations were not altered; however, FSH receptor content was decreased (P less than 0.05) in clomiphene-treated rats proportional to the reduction in testicular weight. In contrast, testicular LH and GnRH receptor concentrations were increased (P less than 0.05) in treated animals, resulting in similar receptor contents. Daily sperm production per gram of parenchyma was unaffected, while daily sperm production per testis was decreased in treated rats (P less than 0.05). These data show early postnatal treatment with clomiphene does not permanently impair pituitary function. Despite reduced testicular mass, normal serum testosterone concentrations and testis LH receptor content of treated rats suggest recovered Leydig cell function. The decreased content of testicular FSH receptors and reduced sperm production suggest seminiferous tubule function was compromised in the adult rat.

Long-term negative feedback effects of oestrogen and progesterone on the pituitary gland of the long-term ovariectomized ewe

The effects of long-term treatment with physiological doses of oestradiol or oestradiol plus progesterone on plasma gonadotrophin levels and pituitary content of LH and gonadotrophin-releasing hormone (GnRH) receptors were studied in ovariectomized-hypothalamo-pituitary disconnected ewes given 250 ng pulses of GnRH every 2 h (i.v.). A pilot experiment showed that 3 cm long Silastic implants (s.c.) reduced both LH pulse frequency and pulse amplitude in long-term (greater than 6 months) ovariectomized ewes. The main experiment was conducted over 3 weeks in ovariectomized-hypothalamo-pituitary disconnected ewes that had received pulsatile GnRH replacement for 1 week after pituitary surgery. Group 1 (n = 5) received GnRH pulses alone throughout the study. Group 2 (n = 6) received oestradiol in week 2 and oestradiol plus progesterone in week 3 and in group 3 (n = 6) the steroid treatments were reversed. Oestradiol reduced (P less than 0.05) the mean (+/- S.E.M.) amplitude of LH in pulses in group 2 (from 8.2 +/- 1.6 to 5.0 +/- 0.5 micrograms/l) and group 3 (from 11.6 +/- 1.2 to 9.3 +/- 1.0 micrograms 1): an additional effect of progesterone was seen in group 2 but not group 3. The amplitudes of the LH pulses did not change in the control ewes. Plasma concentrations of FSH were reduced by approximately 50% by the oestradiol treatments with no additional effects of progesterone. There was no effect of steroidal treatment on pituitary content of LH or pituitary levels of GnRH receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopotency of highly purified porcine FSH and human LH on gonadal function

The gonadotrophin preparations that have been used previously to study different aspects of testis function are of limited purity. We have, therefore, purified existing gonadotrophin preparations further. The demonstration of their purity and biological activity are reported as well as their suitability for in-vivo use. After separation of the subunits of the intact hormones by high-performance liquid chromatography followed by analytical sodium dodecylsulphate-polyacrylamide gel electrophoresis, no contaminating proteins could be detected in either the FSH or LH preparation. After immunoadsorption, contamination by other pituitary hormones (TSH, prolactin, FSH, LH and GH) was found to be less than 0.002% by weight for all the hormones tested. The biological activity of porcine FSH (pFSH) measured in a Steelman-Pohley assay was 150-170 times more potent than the NIH-FSH-P1 reference preparation. The biopotency of human LH (hLH) in the ovarian ascorbic acid depletion test was measured and appeared to be 8100-8300 IU/mg against the 68/40 International Standard. The dose-dependent effects of pFSH and hLH on testis weight and the number of FSH and LH receptors were measured in immature (22-day-old) hypophysectomized rats treated for 7 consecutive days. Treatment with FSH induced a dose-dependent increase in testis weight (threefold) when compared with the control. The concentration and total number of LH receptors were increased (two- to sixfold) in a dose-dependent manner. The number of FSH receptors per testis increased while the number of FSH receptors per mg of protein remained unchanged. Administration of human LH to immature hypophysectomized rats had no effect on either LH or FSH receptors, regardless of the dose administered.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibroblast growth factor regulates the expression of luteinizing hormone receptors in cultured rat granulosa cells

We have investigated the effects of bFGF on both the FSH-induced LH receptor expression and cAMP production in cultured rat granulosa cells. Concentrations of pure FGF, from 10(-12) M to 10(-10) M, progressively inhibit the stimulatory actions of FSH with an ED50 of approximately 4 x 10(-12) M for both parameters. Higher FGF concentrations, from 4 x 10(-10) M to 10(-8) M, lead to a gradual reduction of the growth factor inhibitory effect. The effects of FGF are more prominent on the modulation of LH receptors than on the FSH-induced cAMP production. Moreover, FGF impairs the LH receptor formation induced by cholera toxin or 8-Bromo-cAMP, indicating that the growth factor also acts at a step distal to cAMP formation. The inhibitory effect of FGF on LH receptor expression increases during the entire course of granulosa cell differentiation, from 24 to 96 h, and is not due to variations in cell number or viability, but rather to a change in the content of LH receptors with no significant modification of binding affinity (KD congruent to 0.8 x 10(-10) M). These results suggest that bFGF may acutely regulate the capacity of granulosa cells to differentiate upon FSH stimulation and to respond to LH during the ovarian follicular maturation.

Pituitary and Leydig cell function in boars actively immunized against gonadotrophin-releasing hormone.

Crossbred boars were (a) immunized against GnRH conjugated to human serum globulin (200 micrograms GnRH-hSG) in Freund's adjuvant at 12 weeks of age and boosted at weeks 18 and 20 (N = 10), (b) served as controls and received hSG only in adjuvant (N = 10), or castrated at weaning (N = 10). At 24 weeks of age (immediately before slaughter), the boars were challenged with saline or pig LH (1 microgram/10 kg body weight). After slaughter, fresh testicular fragments were incubated with pig LH (0.05 and 0.2 ng/2 ml medium) to assess the effects of immunization on Leydig cell function. Pituitary contents of LH and FSH, and testicular LH receptor content were also measured. The results indicated that plasma LH and testosterone concentrations, pituitary LH content, testicular LH receptor content, testis and sex accessory organ weights were significantly reduced in GnRH-immunized boars compared to hSG-adjuvant controls. However, plasma and pituitary FSH content were not affected by high antibody titres generated against GnRH. The testicular testosterone response to exogenous LH in vivo and in vitro was significantly reduced (P less than 0.05) in GnRH-immunized boars. These results indicate that active immunization against GnRH impairs pituitary and Leydig cell functions in boars.

Characterization of the effects of clomiphene citrate on reproductive physiology in male rats of various ages.

Clomiphene citrate (clomiphene) inhibits reproduction in male rats; however, stimulatory effects have been reported at low doses. Male rats were implanted at 60 (adult), 35 (peripubertal) or 10 (prepubertal) days of age with pellets that delivered 0, 0.05, 0.5 or 5.0 mg clomiphene.kg-1.day-1 and were sacrificed after 7 or 14 days of treatment. Testis weight was unaffected by clomiphene in adult and peripubertal rats, but was reduced by all doses in prepubertal rats. Seminal vesicle and prostate gland weights were decreased to varying degrees by clomiphene in all animals, except seminal vesicle weight in peripubertal rats. Serum LH and testosterone were decreased by most doses in all age groups, whereas pituitary LH was decreased in prepubertal rats only. Pituitary GnRH and testicular LH receptor concentrations were reduced in all treated animals. Serum and pituitary FSH were decreased in pre- and peripubertal rats, whereas testicular FSH receptor concentrations were unaffected by treatment. In summary, 1) reproductive function was compromised by clomiphene and many responses were age-dependent, 2) reductions in gonadotropins suggest that clomiphene decreased their synthesis and/or release, and 3) decreased serum LH and testicular LH receptor concentrations were coupled to reduced testosterone secretion.