Molecular characterization of three gonadotropin subunits and their expression patterns during ovarian maturation in Cynoglossus semilaevis

The endocrine regulation of reproduction in a multiple spawning flatfish with an ovary of asynchronous development remains largely unknown. The objectives of this study were to monitor changes in mRNA expression patterns of three gonadotropin hormone (GTH) subunits (FSHβ, LHβ and CGα) and plasma GTH levels during ovarian maturation of half-smooth tongue sole Cynoglossus semilaevis. Cloning and sequence analysis revealed that the cDNAs of FSHβ, LHβ and CGα were 541, 670 and 685 bp in length, and encode for peptides of 130, 158 and 127 amino acids, respectively. The number of cysteine residues and potential N-linked glycosylation sites of the flatfish GTHs were conserved among teleosts. However, the primary structure of GTHs in Pleuronectiformes appeared to be highly divergent. The FSHβ transcriptional level in the pituitary remained high during the vitellogenic stage while plasma levels of FSH peaked and oocyte development was stimulated. The LHβ expression in the pituitary and ovary reached the maximum level during oocyte maturation stages when the plasma levels of LH peaked. The brain GTHs were expressed at the different ovarian stages. These results suggested that FSH and LH may simultaneously regulate ovarian development and maturation through the brain-pituitary-ovary axis endocrine system in tongue sole.

Variant-beta luteinizing hormone is not associated with poor ovarian response to controlled ovarian hyperstimulation

BACKGROUND

The most common genetic variant of luteinizing hormone (LH), variant-betaLH, has a different bioactivity than the wildtype. Carrying the variant allele was associated with an increased consumption of exogenous gonadotropin to achieve optimal ovarian response for in vitro fertilization procedures (IVF). The aim of this study was to examine if variant-betaLH was also more common in patients with a poor ovarian response to exogenous gonadotropin which negatively influenced treatment outcome.

FINDINGS

36 patients with poor ovarian response to ovarian stimulation for IVF and 98 controls with a normal response were genotyped for variant-betaLH using DNA sequencing. The carrier frequency in the control group was 17%. No association was found between poor ovarian response and variant-betaLH.

CONCLUSIONS

Testing patients for variant-betaLH prior to IVF is unlikely to predict poor ovarian response.

Free fatty acids induce Lhb mRNA but suppress Fshb mRNA in pituitary LβT2 gonadotropes and diet-induced obesity reduces FSH levels in male mice and disrupts the proestrous LH/FSH surge in female mice

Female obesity is associated with insulin resistance, hyperandrogenemia, and reproductive dysfunction. We hypothesized that elevated free fatty acids (FFAs) might directly modulate pituitary gonadotropin production. FFAs caused a time- and dose-dependent increase in phosphorylation of the MAPKs p38MAPK, c-Jun N-terminal kinase (JNK)-1/2, and ERK1/2 in LβT2 gonadotrope cells. Furthermore, FFAs up-regulated Lhb mRNA expression acutely, an effect that was blocked by JNK inhibition, but suppressed Fshb mRNA expression, an effect that was independent of MAPK signaling. FFAs enhanced the activation of the MAPKs in the presence of GnRH, although the cotreatment did not alter Lhb induction but did eliminate the GnRH induction of Fshb. FFAs also suppressed activin-induced Fshb expression. Knockdown experiments showed that the FFA effect on the inflammatory kinases p38MAPK and JNK and on Lhb, but not Fshb, mRNA expression is mediated via toll-like receptor-2 and toll-like receptor-4 and was mimicked by lipopolysaccharide stimulation. In vivo, male C57BL/6 mice on a high-fat diet showed reduced FSH levels consistent with the suppression of Fshb seen in vitro. Histological analysis of the testes showed an increased number of abnormal seminiferous tubules. Female mice on a high-fat diet lacked the expected proestrus LH and FSH surge and exhibited an increase in the number of days at estrus and a reduced number of days at proestrus, and ovaries had significantly fewer corpora lutea. Taken together, our findings suggest that lipid excess can lead to reproductive defects in both male and female mice.

Hypogonadism in a patient with two novel mutations of the luteinizing hormone β-subunit gene expressed in a compound heterozygous form

CONTEXT

LH gene mutations are rare; only four mutations have been described. The affected individuals are hypogonadal.

PATIENT

We describe the clinical features of a 31-yr-old man who presented with delayed puberty and azoospermia and was found to have hypogonadism associated with an absence of circulating LH.

MAIN OUTCOME MEASURES AND RESULTS

The patient had a 12-bp deletion in exon 2 in the LH β-subunit gene and a mutation of the 5' splice site IVS2+1G→T in the same gene present in a compound heterozygous state. The first mutation predicts a deletion of four leucines of the hydrophobic core of the signal peptide. The second mutation disrupts the splicing of mRNA, generating a gross abnormality in the processing. The patient's heterozygous parents were clinically normal. The phenotype of a 16-yr-old sister of the proband, carrying the same mutations, was characterized by normal pubertal development and oligomenorrhea.

CONCLUSION

This report unravels two novel mutations of the LH gene critical for synthesis and activity of the LH molecule. The insight gained from the study is that normal pubertal maturation in women can occur in a state of LH deficiency, whereas LH is essential for maturation of Leydig cells and thus steroidogenesis, puberty, and spermatogenesis in man. These mutations should be considered in girls and boys with selective deficiency of LH.

Seasonal effect of GnIH on gonadotrope functions in the pituitary of goldfish

Gonadotropin-inhibitory hormone (GnIH) inhibits gonadotropin release in birds and mammals. To investigate its role in teleosts, we examined the effects of synthetic goldfish (g)GnIH on pituitary LH-β and FSH-β subunit, and gGnIH receptor (gGnIH-R) mRNA levels and LH secretion in goldfish. Intraperitoneal injections of gGnIH increased pituitary LH-β and FSH-β mRNA levels at early to late gonadal recrudescence, but reduced serum LH and pituitary gGnIH-R mRNA levels, respectively, at early to mid-recrudescence and later stages of recrudescence. Static incubation with gGnIH elevated LH secretion from dispersed pituitary cell cultures from prespawning fish, but not at other recrudescent stages; suppressed LH-β mRNA levels at early recrudescence and prespawning but elevated LH-β at mid-recrudescence; and consistently attenuated FSH-β mRNA in a dose-specific manner. Results indicate that in goldfish, regulation of LH secretion and gonadotropin subunit mRNA levels are dissociated in the presence of gGnIH and dependent on maturational status and administration route.

Defining global gene expression changes of the hypothalamic-pituitary-gonadal axis in female sGnRH-antisense transgenic common carp (Cyprinus carpio)

Background

The hypothalamic-pituitary-gonadal (HPG) axis is critical in the development and regulation of reproduction in fish. The inhibition of neuropeptide gonadotropin-releasing hormone (GnRH) expression may diminish or severely hamper gonadal development due to it being the key regulator of the axis, and then provide a model for the comprehensive study of the expression patterns of genes with respect to the fish reproductive system.

Methodology/Principal Findings

In a previous study we injected 342 fertilized eggs from the common carp (Cyprinus carpio) with a gene construct that expressed antisense sGnRH. Four years later, we found a total of 38 transgenic fish with abnormal or missing gonads. From this group we selected the 12 sterile females with abnormal ovaries in which we combined suppression subtractive hybridization (SSH) and cDNA microarray analysis to define changes in gene expression of the HPG axis in the present study. As a result, nine, 28, and 212 genes were separately identified as being differentially expressed in hypothalamus, pituitary, and ovary, of which 87 genes were novel. The number of down- and up-regulated genes was five and four (hypothalamus), 16 and 12 (pituitary), 119 and 93 (ovary), respectively. Functional analyses showed that these genes involved in several biological processes, such as biosynthesis, organogenesis, metabolism pathways, immune systems, transport links, and apoptosis. Within these categories, significant genes for neuropeptides, gonadotropins, metabolic, oogenesis and inflammatory factors were identified.

Conclusions/Significance

This study indicated the progressive scaling-up effect of hypothalamic sGnRH antisense on the pituitary and ovary receptors of female carp and provided comprehensive data with respect to global changes in gene expression throughout the HPG signaling pathway, contributing towards improving our understanding of the molecular mechanisms and regulative pathways in the reproductive system of teleost fish.

Components of the porcine anterior pituitary insulin-like growth factor system throughout the estrous cycle

Components of the circulating and anterior pituitary insulin-like growth factor (IGF) system vary in response to steroids in pigs. However, whether serum and anterior pituitary concentrations of the IGF system vary throughout the estrous cycle has not been determined. To further examine this relationship, estrus was synchronized in 40 gilts of similar age and weight (180 d; 120 kg) by feeding 15 mg altrenogest for 15 d to synchronize estrus. Gilts were checked twice daily for expression of estrus beginning 3 d after the end of altrenogest treatment and continuing for 7 d. The first day each gilt exhibited estrus was designated as day 1 of the estrous cycle. Blood samples were obtained by jugular venipuncture on days 1, 4, 7, 10, 13, 16, 19, and 22 of the estrous cycle. On days 7, 13, 19, and 22 of the estrous cycle 10 pigs were killed and anterior pituitary glands (AP) were collected. Serum concentrations of IGF-I and AP concentrations of IGF-I were determined by radioimmunoassay. Relative amounts of AP IGF binding protein (IGFBP) were determined by western ligand blot analysis. Relative expression of AP IGF-I, IGF-I receptor (IGF-I-R), gonadotropin-releasing hormone receptor (GnRHR), and luteinizing hormone (LH)-β subunit were determined by real-time reverse transcription polymerase chain reaction. Serum concentrations of IGF-I fluctuated throughout the estrous cycle. Mean serum concentrations of IGF-I decreased (P < 0.02) from day 1 through day 10, increased (P < 0.02) on days 13 through 16, and then decreased (P < 0.02) from days 19 through 22. Mean AP concentrations of IGF-I were greater (P < 0.03) on day 19 than on all other days, whereas no difference was detected (P > 0.05) in mean AP concentrations of IGF-I on days 7, 13, and 22. Mean relative amounts of AP IGFBP-2 and -5 were each greater (P < 0.02) in gilts on day 19 than on all other days, whereas no difference was detected (P > 0.05) in mean relative amounts of AP IGFBP-2 and -5 among pigs on days 7, 13, and 22 of the estrous cycle. Relative expression AP IGF-I was greater (P < 0.05) on days 13, 19, and 22 than on day 7 of the estrous cycle. Similarly, the relative expression of AP IGF-IR was increased (P < 0.05) in gilts on days 13, 19, and 22 compared with day 7. The relative expression of GnRHR was greater (P < 0.05) on days 13 and 22 of the estrous cycle than on day 7. The relative expression of LHβ subunit was greater (P < 0.05) on day 19 of the estrous cycle than on days 7, 13, and 22. Anterior pituitary release of LH throughout the porcine estrous cycle may be modulated by changes in the intrapituitary IGF system.

Plasticity of the reproductive axis caused by social status change in an african cichlid fish: I. Pituitary gonadotropins

Social position in a dominance hierarchy is often tightly coupled with fertility. Consequently, an animal that can recognize and rapidly take advantage of an opportunity to rise in rank will have a reproductive advantage. Reproduction in all vertebrates is controlled by the brain-pituitary-gonad axis, and in males of the African cichlid fish Astatotilapia burtoni, GnRH1 neurons at the apex of this axis are under social control. However, little is known about how quickly social information is transformed into functional reproductive change, or about how socially controlled changes in GnRH1 neurons influence downstream actions of the brain-pituitary-gonad axis. We created an opportunity for reproductively suppressed males to ascend in status and then measured how quickly the perception of this opportunity caused changes in mRNA and protein levels of the pituitary gonadotropins. mRNA levels of the β-subunits of LH and FSH rose rapidly in the pituitary 30 min after suppressed males perceived an opportunity to ascend. In contrast, mRNA levels of GnRH receptor-1 remained unchanged during social transition but were higher in stable dominant compared with subordinate males. In the circulation, levels of both LH and FSH were also quickly elevated. There was a positive correlation between mRNA in the pituitary and circulating protein levels for LH and FSH, and both gonadotropins were positively correlated with plasma 11-ketotestosterone. Our results show that the pituitary is stimulated extremely rapidly after perception of social opportunity, probably to allow suppressed males to quickly achieve reproductive success in a dynamic social environment.

The intrapituitary endocrine events during maturation and timing of puberty in the female sheep

The aim of this study was to determine the maturational activity of gonadotroph cells, the site of synthesis, storage and release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in Polish Merino female sheep born after the summer solstice. The actual time of puberty of these lambs was delayed until the following breeding season, when they were 14 months old. Changes were examined in 12 peripubertal (30-, 52-week-old) and pubertal (Days 15 and 17 of the second ovarian cycle) females. Histomorphological and functional changes in the gonadotroph population were assayed with hybridohistochemistry, immunohistochemistry, computer-assisted image analysis and radioimmunoassay. The percentage of the adenohypophyseal area (PAA) occupied by gonadotrophs containing LHbeta-mRNA was higher and the LH plasma concentration and pulse frequency were lower in the 52-week-old sheep in comparison with the 30-week-old sheep (P<0.05). The PAA occupied by immunoreactive (ir)-LHbeta-cells remained stable at the 30th and 52nd weeks of age and then increased at the pubertal follicular phase. The PAA occupied by ir-FSHbeta-cells was higher in the 52-week-old sheep compared with the 30-week-old sheep and then lower at the pubertal follicular phase (P<0.05). The PAA occupied by gonadotrophs containing LHbeta-mRNA or FSHbeta-mRNA was lower at the pubertal follicular phase in comparison with the 52nd week of age (P<0.05). In pubertal sheep, the PAA occupied by gonadotrophs containing LHbeta-mRNA or FSHbeta-mRNA was higher and the PAA occupied by ir-LHbeta or ir-FSHbeta-cells was lower at the preovulatory phase in comparison with the follicular phase of the cycle (P<0.05). In conclusion, the photoperiodic suspension of gonadotroph population's maturational functions has been observed at the level of LH storage and release but not at the level of LH synthesis during the expected time of puberty in female sheep of an aseasonal breed such as Merino. The findings show the heterogeneity in the patterns of LH and FSH post-transcriptional processing during the period of peripubertal/pubertal transition, explained by the different intrapituitary regulation at the level of post-transcriptional synthesis and storage rather, than at the level of release. Altogether, intrapituitary mechanisms of ovine maturation could have the histomorphological feature. Our observations prompt the hypothesis that the female lamb may be able to transduce changes in day length into the appropriate endocrine cues for sexual maturation after attainment by the pituitary gonadotroph population the full peripubertal efficiency, manifested by the sufficient storage of LH.

Effects of a depot formulation of the GnRH agonist leuprorelin on the ultrastructure of male rat pituitary gonadotropes

To clarify the acute and chronic effects of GnRH agonists on pituitary gonadotropes, changes in the ultrastructure of male rat gonadotropes were examined immunocytochemically and morphometrically after the administration of a one-month depot formulation of the GnRH agonist, leuprorelin. Immediately after the depot administration, the relative amounts of secretory granules drastically decreased in gonadotropes concomitantly with a marked increase in the plasma LH level. After the acute hyperstimulated phase, secretory granules in gonadotropes were gradually restored although the newly synthesized granules were less densely immunolabeled for LHbeta; their relative amounts and sizes were still significantly smaller than the controls after depot treatment for 28 days. Eighty-four days after the leuprorelin depot administration, however, the ultrastructural characteristics of pituitary gonadotropes appeared to recover as observed in controls: there were no significant differences in the relative amounts, sizes, and labeling densities for LHbeta of secretory granules, and the amounts of chromogranin A (CgA) and secretogranin II (SgII) were restored in secretory granules to control levels. When the rats were repeatedly treated with the leuprorelin depot at intervals of 4 weeks, the expression and intracellular storage levels of gonadotropins remained highly suppressed, judging from the labeling density for LHbeta. These findings suggest that the depot formulation of the GnRH agonist could suppress both the biosynthesis and release of gonadotropins for a month by synergistically depleting the intracellular storage of secretory granules at the onset of the treatment and by inducing the subsequent desensitization of the GnRH receptor signaling.

Effects of long-term treatment with resveratrol and subcutaneous and oral estradiol administration on pituitary function in rats

Hormone replacement therapy (HRT) has been used for several decades to treat menopausal discomforts. However, in the light of recent studies that draw attention to the potential hazards of conventional HRT, various attempts have been undertaken to search for alternatives to classical HRT. Phytoestrogens are claimed to be capable of positively influencing menopausal symptoms, including hot flushes. We designed a long-term study of 3 months to assess the effects of subcutaneous and orally fed 17beta-estradiol (E2), as well as the actions of resveratrol (RES) on pituitary function in female rats. Our results have demonstrated that RES binds with a 10-fold lower affinity to estrogen receptor (ER)-alpha than to ERbeta. The data from the in vivo study revealed that a dosage of 5 microg and 50 microg RES/kg bodyweight per day given to ovariectomized (OVX) rats achieved serum levels of 1.0 and 8.1 microM respectively. Long-term treatment of OVX rats with RES revealed no estrogenic potential on pituitary function in vivo as assessed by LH and prolactin secretion and by regulation of mRNAs for LHalpha, LHbeta, and GnRH receptor. Subcutaneous treatment with E2 in silastic capsules exerted stronger effects on LH and prolactin secretion, as well as on LHbeta, LHalpha, GnRH receptor, and ERbeta mRNA regulation compared with orally applied estradiol benzoate despite comparable serum levels. Levels of aryl hydrocarbon receptor (AhR) mRNA in the pituitary were increased following OVX and attenuated by long-term E2 treatment, whereas RES did not modulate AhR mRNA expression.

Frequency of the allelic variant (Trp8Arg/Ile15Thr) of the luteinizing hormone gene in a Brazilian cohort of healthy subjects and in patients with hypogonadotropic hypogonadism

PURPOSE

To evaluate the frequency of allelic variant Trp8Arg/Ile15Thr in the luteinizing hormone beta-subunit gene in a Brazilian population of healthy subjects and in patients with hypogonadotropic hypogonadism.

SUBJECTS AND METHODS

Two hundred and two adults (115 women) with normal sexual function and 48 patients (24 women) with hypogonadotropic hypogonadism underwent a molecular study of the the luteinizing hormone beta-subunit gene using a polymerase chain reaction technique followed by enzymatic digestion with the restriction enzymes Nco I (for detection of the Trp8Arg point mutation) and Fok I (for detection of the Ile15Thr point mutation). Basal luteinizing hormone and FSH, testosterone, or estradiol levels were measured in 37 healthy subjects (21 women) and in 27 hypogonadotropic hypogonadism patients (13 women) by immunofluorometric methods (hLH-Spec and hFSH-Spec, AutoDELFIA, Wallac Oy, Turku, Finland).

RESULTS

The genetic variant of the luteinizing hormone beta-subunit gene was present at a similar frequency in healthy subjects (14.4%) compared to patients with hypogonadotropic hypogonadism (16.6%). There was no effect of the allelic variant of the luteinizing hormone beta-subunit gene on luteinizing hormone levels in patients with hypogonadotropic hypogonadism as compared to healthy subjects.

CONCLUSION

This study indicates that the allelic variant Trp8Arg/Ile15Thr of the luteinizing hormone beta-subunit gene is a common polymorphism in the Brazilian population (14.4%). The same frequency of this luteinizing hormone variant in the groups with hypogonadotropic hypogonadism and in the healthy subjects excludes a relationship between this variant and hypogonadotropic hypogonadism.

The effect of Nestorone on gonadotropic cells in pituitary of rats

The implant containing Nestorone is a promising long-acting contraceptive especially suitable for lactating women. In this study, two experiments were designed to observe the effect of Nestorone on the gonadotropic cells in pituitary of rats for analyzing its antiovulation mechanism. In the first experiment, the ED50 of Nestorone on inhibiting ovulation was found to be 1.32 mg/kg. The serum luteinizing hormone (LH) levels were significantly lower 60 h after being treated with Nestorone at 8:30-9:00 a.m. on Day 2 (D2) of estrus. Image analysis showed that the average size of the LH cells in groups treated with Nestorone at 2 or 4 mg/kg was larger than that of the control. In the group treated with 4 mg/kg, most of gonadotropic cells were regular round in shape. And, abundant granules in cytoplasm were found in those cells, which indicated that the LH stored in cells was not released. In the second experiment, the rats were treated with Nestorone at 5 mg/kg at 11:30-12:00 a.m. on D2 of estrus. The normal or higher expression of LHbeta mRNA in pituitary suggested that the synthesis of LH was not inhibited by the treatment with Nestorone. The expression of PR mRNA in pituitary was significantly lower than that of the control at 33 h after treatment. This might be a direct effect of Nestorone, since there were no differences in the serum E2 and P4 levels between the treated and the control group. It is concluded that Nestorone prevents ovulation through inhibition of LH secretion and it has no effect on synthesis of LH. Progesterone receptors in pituitary might be involved in this process, but further study is needed to gain more evidence.

Gonadotropin-Releasing Hormone Receptor Gene Expression During Pubertal Development of Female Rats1

Appropriate expression of the GnRH receptor (GnRH-R) in gonadotrophs is critical for GnRH signaling and hence for gonadotropin secretion and sexual development. In the present work, we have studied the ontogeny of the steady-state GnRH-R mRNA levels in pituitaries of female rats from Day 5 to Day 55, when sexual maturity is attained. Developmental changes of gonadotropin subunit (alpha, FSHbeta, and LHbeta) mRNA levels were also assessed. In addition, the role of the endogenous GnRH on the maturational changes of GnRH-R and gonadotropin subunit gene expression was investigated. Messenger RNA levels were determined by Northern blot analysis of total RNA from anterior pituitaries. Amounts of the most abundant (5.0 kilobase [kb]) GnRH-R mRNA increased slowly from Day 5 through the infantile period, to peak at Day 20 ( approximately 4-fold increase vs. Day 5). Thereafter the levels of the GnRH-R mRNA decline abruptly by Day 25 (75% decrease vs. Day 20) and then fell slightly until Day 35. Parallel changes were observed on the 4.5-kb transcript of the GnRH-R gene. Alpha subunit mRNA was easily detected at Day 5 and its levels increased quickly through the beginning of the infantile period to peak at Day 10 (3.2-fold increase vs. Day 5); then it decreased by 85% at Day 35. FSHbeta and LHbeta mRNA levels rose slowly until Days 15-20, a short time before GnRH-R. Thereafter, the levels of both mRNAs fell until Day 35 (90% decrease vs. Day 15 for FSHbeta and 50% decrease vs. Day 20 for LHbeta). To ascertain whether developmental activation of the GnRH-R and gonadotropin subunit gene expression is GnRH dependent, we have studied the effect of blocking the endogenous GnRH action by treating developing female rats with the specific GnRH antagonist cetrorelix (1.5 mg/kg body weight/wk, s.c.) through the infantile (Days 5-20) and the juvenile period (Days 20-35). Cetrorelix completely blocked the rise of levels of the two most abundant species, 5.0 kb and 4.5 kb, of GnRH-R mRNA during the infantile phase and dropped them to almost undetectable levels during the juvenile prepubertal period. Cetrorelix also abolished the developmental rise of gonadotropin beta subunit mRNAs during the two periods of the study. In contrast, alpha subunit gene expression tended to decrease, but not significantly, with cetrorelix treatment during the two periods. These data demonstrate that sexual maturation of female rats is advanced by an early and strong induction of GnRH-R and gonadotropin subunit gene expression during the infantile period, followed by weaker persistent activation during puberty. Developmental GnRH-R and gonadotropin beta subunit gene expression is almost entirely GnRH dependent, not only in the juvenile prepubertal stage but also during the infantile period.

Pulsatile luteinizing hormone and follicle-stimulating hormone secretion and gonadotropin subunit mRNA levels in the ovariectomized GPR-4 transgenic rat

Genetic targeting of the cAMP-specific phosphodiesterase 4D1 (PDE4D1) to gonadotropin-releasing hormone (GnRH) neurons in the GPR-4 transgenic rat resulted in decreased luteinizing hormone (LH) pulse frequency in castrated female and male rats. A similar decrease in the intrinsic GnRH pulse frequency was observed in GT1 GnRH cells expressing the PDE4D1 phosphodiesterase. We have extended these findings in ovariectomized (OVX) GPR-4 rats by asking what effect transgene expression had on pulsatile LH and follicle-stimulating hormone (FSH) secretion, plasma and pituitary levels of LH and FSH, and levels of the alpha-glycoprotein hormone subunit (alpha-GSU), LH-beta and FSH-beta subunit mRNAs. In OVX GPR-4 rats the LH pulse frequency but not pulse amplitude was decreased by 50% compared to wild-type littermate controls. Assaying the same samples for FSH, the FSH pulse frequency and amplitude were unchanged. The plasma and anterior pituitary levels of LH in the GPR-4 rats were significantly decreased by approximately 45%, while the plasma but not anterior pituitary level of FSH was significantly decreased by 25%. As measured by real-time RT-PCR, the mRNA levels for the alpha-GSU in the GPR-4 rats were significantly decreased by 41%, the LH-beta subunit by 38% and the FSH-beta subunit by 28%. We conclude that in the castrated female GPR-4 rats the decreased GnRH pulse frequency results in decreased levels of LH and FSH and in the alpha- and beta-subunit mRNA levels.

Altered kinetics of pituitary response to gonadotropin-releasing hormone in women with variant luteinizing hormone: correlation with ovulatory disorders

OBJECTIVE

The LH response of pituitary gland to gonadotropin-releasing hormone (GnRH) stimulation is not well defined in patients with mutant beta-subunit (Trp(8) to Arg(8) and Ile(15) to Thr(15)). Here we compared the relative activities and dynamics of LH secretion in patients with wild-type and variant LH following injection of GnRH.

METHODS

A GnRH stimulation test was performed in 33 patients with ovulatory disorders (patient group) and 29 women with normal ovulatory cycles (control group) heterozygous for the variant LHbeta allele. Blood samples were obtained up to 120 min after GnRH injection. Serum LH response was determined by comparing the results of LH immunoassays using a monoclonal antibody that recognizes wild-type LH only with those of another assay using a polyclonal antibody that recognizes equally both variant and wild-type LH (total LH). The ratio of variant LH to total LH (LH ratio) was used to determine the serum LH status.

RESULTS

The LH ratio in the control group showed the peak 15 min after GnRH injection, while that in the patient group showed the peaks 30-60 min after injection. The LH ratio in the patient group at 120 min after injection was significantly lower than that in the control group. The percent increases in LH ratio in both groups showed the peak 15 min after injection. The patient group had significantly lower changes of LH ratio at 15, 60, 90 and 120 min after GnRH injection compared with that in the control group.

CONCLUSION

Differences in circulatory kinetics of the two types of LH may explain the differences in LH function between patients with ovulatory disorders and women with normal ovulatory cycles.

Effects of Vinclozolin Administration on Sperm Production and Testosterone Biosynthetic Pathway in Adult Male Rat

The effect of vinclozolin (VCZ), used as a fungicide and known to have anti-androgenic effects on spermatogenesis and gene expression in the male rat testis was investigated. In Experiment 1, VCZ (100 mg/kg/day) or flutamide (FM, 25 mg/kg/day) was orally administered to male Holzman rats for six days. 8 days after the last administration (D8), a drastic increase in intratesticular testosterone was detected in FM (4.2-fold over control) but not in VCZ treated animals, whereas on D36 post-administration, both groups showed similar levels. Significant decreases in daily sperm production were seen in both VCZ and FM-treated rats on D36. Semiquantitative RT-PCR analysis with testicular and pituitary mRNAs on D8 revealed that LHbeta and FSHbeta mRNAs were increased in the pituitary by VCZ, as well as by FM. Among the four testicular steroidogenic enzyme genes, cytochrome P450 side chain cleavage (P450scc) and cytochrome P450 17alpha/C(17-20) lyase (P450c17) mRNAs were significantly increased, whereas 17beta-hydroxysteroid dehydrogenase type III (17betaHSD) mRNA was not changed. A significant increase in 3beta-hydroxysteroid dehydrogenase type I (3betaHSD) and a decrease in androgen receptor (AR) mRNA were observed only in FM treated rats. Immunohistochemistry demonstrated intense staining of P450scc in the interstitial cells of VCZ-treated testis on D8. In Experiment 2, hormone levels were measured at 1, 3, 6, 12 and 24 hours after VCZ (100 mg/kg) administration to Sprague-Dawley rats. Serum LH level remained constant for the first 3 hours and started to increase at 6 hrs. In contrast, serum and intratesticular testosterone levels increased 2-fold at 1 hr and maintained the level until 24 hrs. P450c17 mRNA level was 2-fold increased at all periods, whereas no obvious changes were detected in the other steroidogenic enzyme genes. Although not statistically significant, AR mRNA level increased 2-fold, 3 hrs after VCZ administration. These results indicate that VCZ affects the pituitary in a similar manner as FM, but functions differently on testicular gene expression.