Testicular FSH Receptors Research Articles

Immunization against Kisspeptin-54 perturb hypothalamic–pituitary–testicular signaling pathway in ram lambs

Kisspeptin, a peptide product of KISS1 gene, recently identified as essential upstream gatekeeper in hypothalamic-pituitary-gonadal (HPG) axis. This study was designed to investigate the effect of immunization against kisspeptin-54 on hypothalamic-pituitary-testicular signaling pathway. A total of ten intact 56-days-old ram lambs were used and randomized into the treatment and control groups, which were, respectively immunized by kisspeptin-54 based vaccine and the empty plasmid via intramuscular route. We employed indirect enzyme-linked immunosorbent assay and quantitative real-time PCR to characterize the difference in serum kisspeptin, luteinizing hormone, testosterone hormone concentration and mRNA expression of reproductive-related genes in HPG axis across kisspeptin-54 immunized and control ram lambs. Serum kisspeptin, luteinizing hormone and testosterone concentration in the treatment group was lower (p < 0.05) than that of the control group. Compared with the control group, the mRNA expression of the hypothalamic androgen receptor (AR), KISS1, G protein-coupled receptor (GPR54) and gonadotropin-releasing hormone (GnRH) was altered in the immunized group (p < 0.05). Moreover, mRNA expression of pituitary luteinizing hormone beta (LHβ), follicle stimulating hormone beta (FSHβ), and GnRH receptor as well as, testicular LH receptor and FSH receptor, were remarkably lower (P < 0.05) in the treatment group. We concluded that immunization against kisspeptin-54 reduced serum kisspeptin levels thereby, the normal hypothalamic-pituitary–testicular signaling pathway disrupted. This data provides a great insight for the use of kisspeptin to regulate reproduction.

GnRH-agonist implantation of prepubertal male cats affects their reproductive performance and testicular LH receptor and FSH receptor expression

This study was conducted to investigate the effect of GnRH-agonist implantation in prepubertal tomcats on sexual behavior, reproductive performance, and expression of testicular LH receptor (LHR) and FSH receptor (FSHR) and also to compare the testicular characteristics, LHR and FSHR expression between prepubertal and adult tomcats. In experiment 1, 3-month-old tomcats (n = 6/group) were either treated with or left without 4.7 mg deslorelin implants. Semen collection and evaluation were performed just before castration at 48 weeks after treatment; removed testes were analyzed for mRNA and protein expression of LHR and FSHR. We were able to collect semen from six non-treated cats, whereas in treated cats, semen was uncollectable. The results revealed that sexual behavior was absent in the implanted cats throughout the study period. Testicular volume was found to decrease from 30 weeks after treatment onward in the implanted cats compared to the controls (P < 0.05). Semen production was found only in non-implanted cats. Testicular tissue score, seminiferous tubule diameter, and LHR protein expression were found lower in the implanted cats (P < 0.05), but no differences were observed in mRNA expression of LHR and protein expression of FSHR between groups. The mRNA expression of FSHR was higher in the implanted (P < 0.05) compared to control cats. In experiment 2, testes from prepubertal (n = 6) and adult (n = 6) male cats were collected after castration and analyzed for mRNA and protein expression of LHR and FSHR. No differences were observed in the protein expression of LHR and FSHR between the two groups, whereas mRNA expression of FSHR was higher in prepubertal cats (P < 0.05). Testicular and epididymal weight, diameter of seminiferous tubules, and the testicular grade were higher in the adult compared to prepubertal cats (P < 0.05). In conclusion, deslorelin implants suppressed protein expression of LHR and enhanced mRNA expression of FSHR along with suppression of reproductive function without any adverse effects for at least 48 weeks in male cats.

Prenatal testosterone excess alters Sertoli and germ cell number and testicular FSH receptor expression in rams

Exposure to excess testosterone (T) during fetal life has a profound impact on the metabolic and reproductive functions in the female's postnatal life. However, less is known about the effects of excess testosterone in males. The aim of the present study was to evaluate the impact (consequences) of an excess of T during fetal development on mature male testis. The testicular evaluation was by histological analysis and by determination of mRNA expression of the FSH receptor (FSH-R), transforming growth factor-β type I receptor (TβR-I), and two members of the TGF-β superfamily, transforming growth factor-β3 (TGFβ3) and anti-Müllerian hormone (AMH) in males born to mothers receiving an excess of T during pregnancy. At 42 wk of age, postpubertal males born to mothers treated with 30 mg of T propionate twice weekly from day 30 to 90, followed by 40 mg of T propionate from day 90 to 120 of pregnancy (T males), showed higher concentrations of FSH in response to a GnRH analog, a higher number of Sertoli cells/seminiferous tubule cross-section, and a lower number of germ cells/tubules (P < 0.05) than control males (C males) born to mothers treated with the vehicle. The mRNA expression of FSH-R and of TβR-I was higher in T males compared with C males (P < 0.05). Moreover, in T males, AMH expression level correlated negatively with the expression level of TGFβ3. In C males, this latter correlation was not observed. These results suggest that prenatal exposure to an excess of T can negatively modify some histological and molecular characteristics of the mature testis.

Postnatal changes in testicular gonadotropin receptors, serum gonadotropin, and testosterone concentrations and functional development of the testes in bulls

The primary objectives of this study were to follow the temporal patterns of testicular LH and FSH receptor (LH-R and FSH-R) concentrations and affinity (Ka) during sexual maturation in bulls and to see if such patterns could help explain the control of rapid testicular growth that occurs after 25 weeks of age, when serum gonadotropin concentrations are low. Separate groups of Hereford x Charolais calves (n = 6) were castrated every 4 weeks from 5 to 33 weeks of age and at 56 weeks of age. A week prior to castrations, from 5 to 33 weeks of age, blood was collected every 15 min for 10 h. The transition from indifferent supporting cells to Sertoli cells in seminiferous tubules was rapid between 13 and 25 weeks and rapid testis growth occurred after 25 weeks of age. Serum LH and FSH concentrations were transiently elevated at 12 weeks of age (P < 0.05). LH-R concentrations decreased from 13 to 25 weeks of age and increased to 56 weeks of age (P < 0.05). LH-RKa decreased from 9 to 17 weeks of age, increased to 29 weeks of age and declined to 33 weeks of age (P < 0.05). FSH-R concentrations declined from 17 to 25 weeks of age then increased to 56 weeks of age (P < 0.05). FSH-RKa increased from 17 to 25 weeks of age (P < 0.05). High concentrations of gonadotropins and their receptors may be critical to initiate testis growth postnatally and support it after 25 weeks of age in the face of low serum gonadotropin concentrations.

Recognition of follicle stimulating hormone (alpha-subunit) by a recombinant receptor protein domain coded by an alternately spliced mRNA and expressed in Escherichia coli.

To assess the functional significance of putative proteins encoded by alternately spliced mRNA of the sheep testicular FSH receptor, a short form cDNA comprising of the first four exons (117 residues mature protein) was engineered for expression in Escherichia coli. The expressed protein of molecular mass 15 kDa was purified to homogeneity and verified by reaction with an antibody against a synthetic peptide sequence unique to the amino (N)-terminal region FSH receptor. The purified FSH receptor domain protein bound 125I-labeled hFSH in a ligand blot on polyvinylidine difluoride membranes. Further analyses by slot blot revealed high affinity of the immobilized protein with significant reaction at 10 pmol. As the immobilized receptor protein also reacted with structurally related hormones (125I-labeled LH/125I-labeled human chorionic gonadotropin), we confirmed that interaction most probably occurred via the common alpha-subunit of these glycoprotein hormones. Our results reveal that this N-terminal portion of the FSH receptor contain(s) major site(s) for hormone recognition that could be mediated via the alpha-subunit. A rabbit antibody to the receptor inhibited FSH action in receptor bearing cells, revealing the utility of such recombinant FSH receptor protein(s) for modulation of hormone action.

Ontogenesis of LH and FSH receptors in postnatal rabbit testes: age-dependent differential expression of long and short RNA transcripts.

The ontogeny of testicular LH and FSH receptors was studied in New Zealand rabbits from 20 to 180 days postpartum. The concentrations of free receptors (per mg total proteins) were very low at day 20. They increased steeply at day 30 for the LH receptor and at day 50 for the FSH receptor. Three RNA bands (1.2, 2.5 and 3 kb) were repeatedly detected on northern blots for the LH receptor and two bands (1.2 and 2.2 kb) were detected for the FSH receptor. The 1.2 kb band (which cannot give rise to full-length, membrane-anchored receptor) was present throughout the 20-180 day period for each receptor. However, the higher molecular mass bands were nearly undetectable at day 20. The 2.5 and 3 kb bands of the LH receptor increased twofold between day 20 and day 120, while the 2.2 kb band of the FSH receptor increased fivefold between day 20 and day 75. Thus the very low concentrations, or even absence, of the larger transcripts of both LH and FSH receptors were correlated with the inability to detect their cognate protein until 20 days of age. Subsequently, coordinated increases in high molecular mass transcripts and protein were observed for both receptors. Total LH receptor content increased in parallel to the previously reported increase in plasma testosterone between day 65 and day 100. FSH receptor density began to increase steeply at day 50, just at the onset of spermatogenesis. Thus, postnatal testicular development in the rabbit seems to entail the transcription of high molecular mass, translatable transcripts of the gonadotrophin receptors.

Follitropin Signal Transduction: Alternative Splicing of the FSH Receptor Gene Produces a Dominant Negative Form of Receptor Which Inhibits Hormone Action

We have studied the functional properties of an alternately spliced form of sheep testicular FSH receptor cDNA that codes for a protein similar to a previously described active receptor but differs in the carboxy terminus in sequence and is also shorter by 25 residues. The receptor expressed in HEK 293 cells fails to activate adenylate cyclase. Cotransfection of stably expressing cells bearing FSH receptor that activates (Gs) adenylate cyclase with the altered receptor cDNA abrogates hormone response. In cells expressing this cDNA, FSH also inhibited cyclic AMP accumulation induced by non hormonal agents such as forskolin and cholera toxin which bypass the receptor. We propose that this altered receptor is a dominant negative receptor which may be coupled to Giprotein(s) or other inhibitory mechanisms.

A synthetic peptide corresponding to the third cytoplasmic loop (residues 533 to 555) of the testicular follicle-stimulating hormone receptor affects signal transduction in rat testis membranes and in intact cultured rat Sertoli cells

Involvement of the third cytoplasmic (3i) loop (residues 533 to 555) of the rat testicular FSH receptor in the mechanism of FSH signal transduction was examined using light membranes prepared from immature rat testes, monolayer cultures of rat Sertoli cells, and a synthetic peptide strategy. This region of the FSH receptor is structurally related to G protein-activator regions identified in other G protein-coupled receptors. FSHR-(533–555) peptide amide stimulated guanine nucleotide exchange in rat testis light membranes, presumably via its interaction with membrane-associated G protein. The peptide failed to inhibit FSH binding to testis membrane receptors, indicating that the nucleotide exchange effect was not a result of peptide interaction with receptor. When incubated with cultured Sertoli cells from immature rat testes, FSHR-(533–555) peptide amide consistently and significantly inhibited FSH stimulation of cAMP and estradiol biosynthesis, but failed to inhibit forskolin stimulation of each. The peptide effect, therefore, was not due to a direct interaction with adenylyl cyclase. Since FSHR-(533–555) peptide amide did not inhibit FSH binding to membrane receptor, these results imply entry of the peptide into the Sertoli cell, possibly by vesicular internalization or diffusion. Indeed, the inhibitory effects of FSHR-(533–555) peptide amide on FSH-stimulated estradiol biosynthesis were prevented by pretreating Sertoli cells with phenylarsine oxide, an inhibitor of FSH receptor internalization. FSHR-(533–555) was without effect on basal levels of cAMP and estradiol biosynthesis, indicating absence of toxicity at the concentrations tested. Synthetic peptide amides lacking structural criteria associated with G protein activation did not affect guanine nucleotide exchange or FSH-stimulated estradiol levels, even at concentrations significantly higher than used for the receptor-related peptide. Our results are consistent with peptide interaction with signal-transducing G protein. These data suggest that the 3i loop peptide acts as an antagonist of FSH receptor-mediated G protein activation, and inhibits FSH receptor-mediated signal transduction in intact Sertoli cells. The ability of this FSH receptor-related peptide to affect intracellular processes in intact cultured rat Sertoli cells through its apparent interaction with G protein suggests a novel approach for control of FSH action.

A synthetic peptide corresponding to residues 645–653 in the carboxyl terminal cytoplasmic domain of the rat testicular follicle stimulating hormone receptor modulates G protein coupled-receptor signaling in rat testis membranes and in intact cultured rat Sertoli cells

We examined the involvement of the carboxyl terminal cytoplasmic domain (residues 645–653) of the rat testicular FSH receptor in FSH signal transduction utilizing light membranes prepared from immature rat testes, intact cultured rat Sertoli cells, and a synthetic peptide approach. This region of the FSH receptor was selected because of its structural similarity to receptor-G protein contact sites identified in other G protein-coupled receptors. FSHR- (645–653) peptide amide promoted guanine nucleotide exchange in rat testis membranes, presumably via its interaction with membrane-associated G protein, but did not inhibit FSH binding to testis membrane receptors. When incubated with intact cultured Sertoli cells from immature rat testes, FSHR-((645–653) peptide amide consistently and significantly stimulated basal cAMP and estradiol biosynthesis. The peptide had no effect on forskolin stimulation of cAMP and estradiol, but inhibited FSH stimulation of each. Since FSH binding to receptor was unaffected by the peptide, these results suggest peptide interaction with receptor-associated G protein. The effects of FSHR- (645–653) peptide amide on FSH-stimulated estradiol biosynthesis were prevented by pretreating Sertoli cells with phenylarsine oxide, an inhibitor of FSH receptor internalization. These results suggest that peptide effects in intact Sertoli cells were related to peptide entry into the cell, presumably during receptor-mediated endocytosis of FSH, or by diffusion. Synthetic peptide amides not satisfying structural criteria for G protein coupling had no effect on either guanine nucleotide exchange or estradiol biosynthesis, even at concentrations significantly higher than used for FSHR- (645–653) peptide amide. Although the mechanisms involved in the effects of FSHR- (645–653) peptide amide on FSH-stimulated postbinding events are not completely understood, our results are consistent with interaction of the peptide with signal-transducing G protein. The results of this study further suggest that modulation of hormone action by effects on G protein-related events in intact cells is feasible, and that this intervention may offer an approach for control of FSH action at a level other than receptor binding.

Seasonal Variations in Testicular LH, FSH, and PRL Receptors; in Vitro Testosterone Production; and Serum Testosterone Concentration in Adult Male Vizcacha (Lagostomus maximus maximus)

Seasonal changes in the reproductive activity of the adult male vizcacha (Lagostomus maximus maximus), a South American rodent, were investigated. Monthly, for 1 year, the animals were captured during the night near their burrows in the vicinity of San Luis, Argentina. The animals were killed, and samples of blood and the testes were collected. The testosterone serum levels were determined and the testicular tissue was used for biochemical and structural studies. Significant changes associated with seasonal cycles were found. In July-August (winter in South America), a short hibernal period of sexual quiescence, decline in testicular volume, and a significant decrease in serum testosterone were observed. The in vitro testosterone production and testicular LH, FSH, and PRL receptors revealed a significant decrease during this period. During September-November (spring season), recovery was observed, with a significant increase in gonadal activity during April-May (autumn season). During this season, the gonadal volume was increased, the serum testosterone and the in vitro stimulation of testosterone production by hCG (as well as the basal levels) also revealed a significant increase. Correspondingly, the concentration of testicular LH, FSH, and PRL receptors was elevated. These results indicate an increase in parameters related to testicular function. A gradual reduction in the testicular activity was observed in June-July (early winter). Our findings indicate that the male adult vizcacha, under natural conditions, exhibits characteristics of an annual reproductive cycle.

Developmental changes of testicular activin and FSH receptor mRNA and plasma FSH and inhibin levels in the rat

To investigate the changes in the FSH receptor and the activin receptor during sexual maturation in rat testes, we examined the mRNA levels of the receptors by Northern blot analysis. With a full length rat activin receptor cRNA probe in this study, Northern blot analysis revealed two activin receptor mRNAs (6Kb and 3Kb) in testes. The large messenger (6Kb) was low on day 7, and gradually increased by day 35. On the other hand, the small messenger (3Kb) was low on day 7, began to increase on day 21, and had increased dramatically by day 35. Therefore, compared with our previous data, developmental changes in the mRNA of the activin receptor of male and female gonads showed certain differences. The expression of 3Kb activin receptor mRNA in rat testis may be relevant to the stimulated spermatogenesis in this period. 2.4Kb and 5.5.Kb FSH receptor mRNA were revealed on day 7 and decreased to 80% on day 14 and remained at the same level. The Scatchard plots of FSH binding data showed that the binding affinities of testicular FSH were constant at each stage of development. Changes in the mRNA level in FSH receptor were followed by changes in the concentration of FSH receptor in testis. The rise in the plasma FSH level was concomitant with the decrease in the plasma inhibin level by day 14.

Isoelectric charge of recombinant human follicle-stimulating hormone isoforms determines receptor affinity and in vitro bioactivity.

Recombinant human FSH (rhFSH) was obtained by expressing the human FSH alpha- and beta-subunit complementary DNAs in the chinese hamster ovary cell line. Isoforms of rhFSH were resolved into specific isoelectric (pI) fractions by chromatofocusing. rhFSH isoforms ranged from pI 3.0-5.5 with a modal value of pI 4.2. Analysis of the biological activity of specific pI isoforms of rhFSH was undertaken using both the rat granulosa cell aromatase (in vitro) bioassay and a RRA. More acidic isoforms (e.g. pI 3.5) showed significantly lower affinity (P < 0.05) for rat testicular FSH receptors than did the less acidic isoforms (e.g. pI 4.8). Consistent with the receptor binding affinity data, the more acidic fractions resulted in significantly less activation (P < 0.05) of rat granulosa cell aromatase activity, as measured by estrogen production, than did the less acidic isoforms. The observed bioactivities and their correlation with the pI values of the rhFSH isoforms are consistent with observations of differing bioactivities seen in both pituitary and urinary FSH isoforms. These results demonstrate that rhFSH, made in the chinese hamster ovary cell line, is both biologically active and has isoform profiles, and presumably carbohydrate structures, that closely resemble those seen in natural hFSH.

Expression of recombinant human follicle-stimulating hormone receptor: species-specific ligand binding, signal transduction, and identification of multiple ovarian messenger ribonucleic acid transcripts.

The ligand specificity and biochemical properties of the human (h) FSH receptor are poorly characterized due to the low abundance of these receptors and the limited availability of human tissues. Using a fragment of rat FSH receptor cDNA, we screened a human testicular cDNA library and obtained a FSH receptor cDNA covering the entire amino acid-coding region. After transfection of a human fetal kidney cell line (293) with the hFSH receptor cDNA, radioligand receptor analysis revealed the presence of high affinity (Kd, 1.7 x 10(-9) M) FSH-binding sites on the plasma membrane. Both recombinant and wild-type hFSH displaced [125I]hFSH binding, with ED50 values of 25 and 70 ng/ml, respectively, whereas hLH, hCG, and hTSH were ineffective. Although human, rat(r), and ovine FSH as well as equine CG competed for rat testicular FSH receptor binding, only hFSH and rFSH interacted effectively with the recombinant hFSH receptor, suggesting that species-specific ligand recognition exists between human and rodent receptors. After incubation of transfected cells with hFSH, but not recombinant hLH or hCG, a dose-dependent increase (ED50, 10 ng/ml) in extracellular cAMP accumulation was observed, indicating a functional coupling of the expressed human receptor with the endogenous adenyl cyclase. In cells cotransfected with the FSH receptor expression plasmid and a luciferase reporter gene driven by the promoter of a cAMP-responsive gene, treatment with hFSH, but not hCG, resulted in a dose-dependent increase in luciferase activity. Northern blot analysis using a cRNA probe derived from the human receptor cDNA indicated the presence of multiple FSH receptor mRNA transcripts (7.0, 4.2, and 2.5 kilobases) in RNA prepared from human follicular phase ovary, but not from human corpus luteum or placenta. Additionally, two FSH-binding sites of 76 and 112 kilodaltons were detected in transfected 293 cells after ligand/receptor cross-linking and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. These results demonstrate the expression of functional hFSH receptor with unique ligand specificity and provide new data on the biochemical properties of the human receptor at the mRNA and protein levels.

Differences in properties of the sheep testicular LH and FSH receptors

Differences in binding and structural properties of ovine testicular FSH and LH receptors were investigated. The ovine FSH receptor did not discriminate between FSH of different species, although equine FSH was more reactive. In the same tissue, however, the LH receptor showed marked preference for ovine and bovine LH, reacting very weakly with other preparations of pituitary LH. Human chorionic gonadotrophin also reacted partly with the ovine LH receptor at 25 degrees C. However, at 4 degrees C, the optimum temperature for binding of the LH receptor to its homologous hormone, the receptor displayed no recognition for chorionic gonadotrophin preparations. Affinity cross-linking studies with ovine testicular membrane suggested that the ovine FSH receptor has an Mr of 70,000, which is very similar to that observed in the porcine ovary. The Mr of the ovine LH receptor was estimated to be 150,000, which is different from those of other mammalian species, including those that have been cloned. The data suggest that the binding and structural properties of the ovine FSH receptor are similar to those of other mammalian FSH receptors, whereas the ovine LH receptor appears to differ from other mammalian LH receptors in having a different Mr and in being more stringent in its requirement for pituitary LH.

Pituitary and Gonadal Hormone-Dependent and - Independent Induction of Follicle-Stimulating Hormone Receptors in the Developing Testis

The number of FSH receptors increases during testicular development in several species of mammals. Hypophysectomy and hormonal replacement were performed to identify the factors that induce developmental changes in testicular FSH receptors. Male rats of the Wistar/Tw strain were hypophysectomized at 9, 16, 23, or 30 days or 3 months of age. These rats were killed 10 days after surgery along with intact control rats, and the testes were removed for receptor assay. A group of intact rats was killed on the day of surgery as initial controls. All of the hypophysectomized immature rats showed a higher density of FSH binding (FSH binding per unit weight) and a lower total FSH binding (FSH binding per two testes) compared with each of the matched intact control rats. In contrast to FSH binding, not only the total LH binding but also the density of LH binding were invariably lower in the hypophysectomized rats than in the intact control rats. Unlike hypophysectomy at other immature ages, surgery at 9 days of age was followed by significant increases in testicular weight, density of FSH binding, and total FSH binding compared with those values in the initial control rats. There was no significant effect of hypophysectomy on total FSH binding in adult animals, in contrast to the marked decrease in total LH binding. When male rats hypophysectomized at 25 days of age were injected with FSH for 5 days beginning on the 11th day after surgery, dose-dependent increases in total FSH binding and testicular weight were observed. Testosterone treatment induced an increase only in the total FSH binding, but its effect was less potent. Scatchard plot analyses of the binding suggested that changes in FSH binding with age, after hypophysectomy, and after hormonal administration were due to changes in the number of binding sites. Plasma FSH concentrations in all postoperative rats were below or at the level of detectability, indicating that hypophysectomy was successful. In normal immature rats, a significant increase in the plasma FSH level was detected only from 9-19 days of age, in contrast to the continuous increase in total FSH binding during testicular development. These results suggest that FSH and testosterone act as hormonal factors to induce an increase in the number of FSH receptors in the developing testis. Other factors that are independent of pituitary and sex hormones may also contribute to FSH receptor induction.

Correlative Morphology and Endocrinology of Sertoli Cells in Hamster Testes in Active and Inactive States Spermatogenesis*

The seasonally breeding golden (Syrian) hamster, which exhibits photoperiod-dependent transitions between active and inactive states of spermatogenesis, was used as a model to study Sertoli cell structure in the two extreme phases of gonadal activity. The structural parameters of the Sertoli cell and its subcellular organelles were assessed using accepted stereological procedures during active and inactive states of spermatogenesis, and the results correlated with a battery of endocrine parameters obtained from the same animals. Short photoperiod-induced testicular involution was associated with a significant decrease in virtually all morphological parameters of the Sertoli cell, including a dramatic decrease in the volumes and surface areas of the Sertoli cells and their major subcellular organelles. Sertoli cell size and surface area were significantly and positively correlated with the testicular weight, volume of the seminiferous tubule, tubular lumena, tubule diameter, and germ cell numbers. Similar correlations were recorded between the number of germ cells and nearly all subcellular parameters of the Sertoli cell. Only those structural elements that are related to degredative processes (lysosomes and lipid) did not show significant volumetric differences between gonadally active and inactive animals. The observed changes in the structural parameters of the Sertoli cells were significantly correlated with the reduction in plasma levels of FSH, LH, and testosterone and intratesticular levels of testosterone. Exposure of hamsters to a short photoperiod was also associated with an increase in concentration (femtomoles per mg protein), but a decrease in the total content (femtomoles per testis) of testicular FSH receptors. The dissociation of changes in the content and concentration of FSH receptors appears to be related to changes in basal compartment plasma membrane surface areas of the Sertoli cells during testicular regression. The striking changes in Sertoli cell morphology between active and inactive states of spermatogenesis are structural manifestations of alterations in the function of these cells in response to the concomitant endocrine changes in the testis and indicate a virtual shut-down of Sertoli cell function during short photoperiod-induced testicular regression.

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.

Testicular FSH and hCG Receptors in Sertoli-Cell-Only Syndrome

Testicular FSH and hCG receptors were measured in patients with Sertoli-cell-only syndrome (SCOS), and the value of Bmax for each hormone was compared with the value in subjects with normal testes. FSH receptor was detectable in only four of 10 patients, and the mean value of Bmax in four of the 10 patients was clearly lower than that in normal testes (p less than 0.005). On the other hand, hCG receptors were detected in all of six tested patients, and the mean value of Bmax was lower, but not remarkably so, than that in the normal testes. The function of Sertoli cells was remarkably impaired in most men with SCOS, whereas the function of Leydig cells was relatively preserved.

Endocrine parameters, hormone receptors, and functions of the testicular interstitium and seminiferous epithelium in estradiol-immunized Ile-de-France rams.

The testicular response of Ile-de-France rams actively immunized against estradiol (E2) was evaluated during both the ovine nonbreeding season (spring) and breeding season (autumn). Plasma concentrations of LH, FSH and testosterone were elevated in E2-immunized rams during both spring and autumn when compared with BSA-immunized controls. Testis weights were significantly elevated by E2 immunization and were characterized by greater interstitial cell volume, including Leydig cells, blood and lymph vessels, greater seminiferous tubule length, and greater numbers of leptotene spermatocytes and round spermatids. Neither Sertoli cell number, Sertoli cell nuclear volume nor testicular FSH receptor number were affected by E2 immunization, but testis weight, Sertoli cell nuclear area, FSH receptor number and LH receptor number were significantly greater in autumn than in spring. A positive effect of E2 immunization on testicular LH receptors was evident in spring but not in autumn. Testicular androgen receptors were suppressed by E2 immunization but were not affected by season. It was concluded that E2 immunization results in moderate stimulation of the ovine testis to increase testosterone secretion and to enhance total daily spermatid production. This effect appears to result from a change in E2 negative feedback and increased pituitary gonadotropin secretion.

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.