Immunoreactive LH Research Articles

Neuropeptide Y and luteinizing hormone releasing hormone synergize to stimulate the development of cellular follicle-stimulating hormone in the hamster adenohypophysis.

Luteinizing hormone releasing hormone (LHRH) stimulates the development of cellular FSH immunoreactivity in the perinatal hamster adenohypophysis. Because neuropeptide Y (NPY) can act directly on rat adenohypophysial cells to stimulate FSH and LH release and potentiate the stimulatory effect of LHRH on FSH and LH release, we investigated the effects of NPY alone and in combination with a low, ineffective dose of LHRH on inducing cellular FSH immunoreactivity in the neonatal hamster adenohypophysis. Neonatal female pituitary glands were grafted beneath the right renal capsules of hypophysectomized-ovariectomized adult hamster hosts with a catheter implanted in the external jugular vein. After treatment, hosts were decapitated and graft tissue was stained for FSH and LH immunoreactivity. The mean percentage of adenohypophysial cells that stained for FSH was low (2.8%) in grafts in hosts infused continuously with heparinized saline vehicle for 7 days. In other hosts, peptides were pulsed through the catheter every 12 h for 7 days. The mean percentage of FSH cells also was low after pulsing 6 ng LHRH or 2 micrograms NPY but increased substantially when the two peptides were pulsed simultaneously. No differences in the mean percentage of LH cells existed between any of the groups. The results demonstrate that NPY and LHRH can synergize to induce cellular FSH immunoreactivity in the neonatal female hamster.

Delayed puberty in males with β-thalassemia major: pulsatile gonadotropin-releasing hormone administration induces changes in gonadotropin isoform profiles and an increase in sex steroids

Patients with beta-thalassemia major often have pubertal delay, the etiology of which has not been fully elucidated. We investigated the pituitary-gonadal response to short-term subcutaneous pulsatile gonadotropin-releasing hormone (GnRH) administration (150 ng/kg body weight every 120 min for 7 days) in five young males (aged 13.6-19.0 years) affected by beta-thalassemia major and presenting signs of delayed puberty. Immunoreactive and bioactive gonadotropin levels were determined and their isoform profiles were examined, before and after GnRH treatment, in a pool of samples collected every 15 min for 240 min. Testosterone, androstenedione, 17-hydroxyprogesterone, dehydroepiandrosterone and 17 beta-estradiol were measured as markers of gonadal function on days 0, 1, 3, 5 and 7 of treatment. Five patients (aged 16.9-26.8 years) with confirmed diagnosis of idiopathic hypogonadotropic hypogonadism who were starting pulsatile GnRH therapy were also studied in the same protocol. Increased sex steroid levels were observed in both groups as a result of treatment. On day 7, the thalassemic patients had increased bioactive luteinizing hormone (LH) and follide-stimulating hormone (FSH), although immunoreactive LH and FSH were comparable to day 0. Moreover, fewer acidic and more basic immunoreactive and bioactive isoforms were noted in LH profiles on day 7. Similar results were observed in hypogonadal patients, who also had increased immunoreactive LH and FSH values. We suggest that the early stage of delayed puberty in thalassemia might be characterized by a neuroendocrine dysfunction resulting in an impaired hypothalamic GnRH release, which is inadequate for a proper pituitary stimulation. Pulsatile GnRH treatment seems to re-establish partially the correct pituitary-gonadal function.

Endocrinology: Reduced implantation rate associated with a subtle rise in serum progesterone concentration during the follicular phase of cycles stimulated with a combination of a gonadotrophin-releasing hormone agonist and gonadotrophin

Our objective was to assess the effects of subtle increases in serum progesterone concentration (1.0-2.0 ng/ml) on the outcome of in-vitro fertilization (IVF), particularly on the quality of embryos, during the follicular phase of cycles stimulated with gonadotrophin-releasing hormone agonist (GnRHa) and human menopausal gonadotrophin (HMG). A total of 97 patients underwent 116 cycles of IVF and were stimulated with a combination of HMG and GnRHa. They were divided into two groups: those with a subtle progesterone rise and those with no progesterone rise. The two groups were compared with respect to serum oestradiol, progesterone, immunoreactive luteinizing hormone (I-LH), bioactive LH (B-LH), and results of IVF. The groups did not differ significantly in mean age or in total dose of HMG received. On the day that human chorionic gonadotrophin was administered, concentrations of oestradiol and progesterone were significantly higher in the subtle progesterone rise cycles than in the no progesterone rise cycles. In the no progesterone rise cycles, the percentages for embryos beyond the 4-cell stage, grade 1 embryos, and implantation rates were significantly higher than those in subtle progesterone rise cycles. The combination of GnRHa and HMG eliminated any significant rise in serum I-LH or B-LH concentration during the follicular phase, but did not suppress the subtle rise in progesterone. These results confirm our previous finding that a subtle progesterone rise adversely affects the outcome of IVF. It is also suggested that a reduction in embryo quality may influence the lower rate of implantation in subtle progesterone rise cycles.

Age related changes in the pituitary‐testicular axis in normal men; lower serum testosterone results from decreased bioactive LH drive

The mechanism underlying the slight hypoandrogenism associated with normal ageing remains unclear. We have therefore examined age related changes in the activity of the pituitary-testicular axis in healthy normal males. Random blood samples were obtained from 219 normal men whose ages ranged from 20 to 79 years. At the time of the study, none of the men had received treatment or had ever had any endocrine dysfunction diagnosed. Luteinizing hormone was measured in the subjects' plasma using a commercially available immunoradiometric assay (IRMA, Serono Maiaclone) and a fully validated in-vitro bioassay. Testosterone and FSH were measured using standard radioimmunoassays (RIA) whilst sex hormones binding globulin was assayed by an IRMA. Levels of total testosterone (total-T) and bioactive LH fell with age (r = -0.231 and -0.189 respectively) by 5.9 nmol/l and 2.3 IU/l respectively between grouped patients aged 20-39 years (Group A) and 60-79 years (Group C). In contrast, immunoreactive LH remained unchanged. The LH B:I ratio also fell with age (P < 0.0001) being 5.0 +/- 0.3 (group A) and 3.3 +/- 0.2 (group C), representing a fall of 33%. Since immunoreactivity remained constant, this fall primarily represented the decline in LH bioactivity. Bioactive, but not immunoreactive LH correlated to total-T (P = 0.009, n = 209) and the total-T:LH ratios fell by over 30% between groups A and C using the IRMA, but remained unchanged by bioassay. There is an underlying decline in both total-testosterone and free-testosterone index, and bioactive LH levels with advancing age, suggestive of a hypothalamo-pituitary defect which leads to lower bioactive LH levels which in turn are responsible for the diminished gonadal steroidogenesis. Elucidation of the mechanism underlying this slight decline in hypothalamopituitary testicular activity is complicated by differences between the data obtained by immunoassay or bioassay.

Ovarian Stromal Hypertrophy in Hyperandrogenic Women

Dewailly, Didier; Robert, Yann; Helin, Isabelle; Ardaens, Yves; Thomas-Desrousseaux, Patricia; Lemaitre, Laurent; Fossati, PierreAuthor Information

Occurrence and biological properties of a common genetic variant of luteinizing hormone.

We have characterized the frequency and selected biological properties of a variant form of LH caused by two point mutations in the gene of the LH beta-subunit. Detection of the LH variant (or polymorphism) is based on aberrant immunoreactivity; it is not detected by a monoclonal antibody (Mab) recognizing a specific epitope in the LH alpha/beta-dimer (assay 1), but an assay using two LH beta-specific Mab recognizes this LH form normally (assay 2). Hence, the ratio of LH measured by assays 1 and 2 is 1.18-2.10 (range of mean +/- 2 SD) in wild-type subjects, 0.54-0.98 in heterozygotes, and below 0.15 in homozygotes with regard to the mutant LH beta allele. Analysis of sera from 249 healthy male and female subjects of Finnish origin revealed a frequency of 24.1% heterozygotes and 3.6% homozygotes for the mutation, with similar proportions in each sex. The ratio of in vitro bioactivity to immunoreactivity (assay 2) of the variant LH was significantly (P < 0.01) increased (2.9 +/- 0.1; n = 11) compared to that of wild-type LH (2.2 +/- 0.1; n = 13). No difference was observed in LH pulsatility, measured from blood samples collected at 5-min intervals for 5 h, between three male and three female subjects homozygous for the LH variant and three matched male and three female controls with wild-type LH. Likewise, the responses of LH immunoreactivity (assay 2) to GnRH stimulation were similar with both types of LH. The half-time of the variant LH in rat circulation from both sexes was significantly shorter than that of LH from control subjects (males, 25.5 +/- 3.8 vs. 48.3 +/- 2.7 min, respectively; P < 0.01; n = 3). Upon isoelectric focusing of peripheral serum samples, the isoform distribution of the variant LH was similar to that of wild-type LH. In conclusion, the LH variant discovered by us appears to occur with high frequency in the Finnish population (28% homo- or heterozygotes). It has increased in vitro bioactivity and a decreased half-time in vivo. These differences are compatible with a putative extra carbohydrate chain in the LH beta-chain, as one of the two mutations introduces an extra glycosylation signal. The subjects homozygous for the LH polymorphism are apparently healthy. However, the altered bioactivity and in vivo kinetics of the LH variant may induce subtle changes in LH action, either predisposing the affected individuals to or protecting them from disease conditions related to LH action.

Expression of gonadotrophin subunit genes in sheep that were homozygous carriers and non-carriers of the Booroola fecundity gene FecB.

Homozygous carriers (BB) of the Booroola fecundity gene FecB are characterized by high plasma concentrations of immunoreactive or biologically active FSH and, to a lesser extent, of immunoreactive LH, relative to non-carriers (++). Bovine cDNA probes for the alpha gonadotrophin, FSH beta and LH beta genes were used to investigate FecB-specific differences in the mRNA species for the gonadotrophin subunits in pituitaries obtained from ++ and BB mid-luteal phase ovary-intact ewes, ovariectomized ewes and ovary-intact or ovariectomized ewes with hypothalamic-pituitary disconnection (HPD) given the same regimen of pulsatile GnRH. No FecB-specific differences in the number or size of mRNA transcripts detected by northern blotting were noted for any of these genes. Densitometry of the northern blots revealed no significant FecB-specific differences in the relative amounts of mRNA encoding alpha gonadotrophin, FSH beta or LH beta in the pituitaries from any of the experimental groups of ++ and BB sheep. Furthermore, there were no significant FecB-specific differences in the pituitary content of FSH or LH in these animals, despite significantly higher plasma concentrations of FSH in the ovary-intact and ovariectomized HPD groups. These data show that whereas the FecB gene causes increased plasma concentrations of FSH, no consistent effects can be demonstrated on pituitary gonadotrophin content or on gonadotrophin subunit gene transcription, using northern analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of corticosterone and testosterone on pituitary gonadotropin content, secretion, bioactivity and messenger RNA levels in the presence or absence of GnRH in male rats

The effects of corticosterone (B) and testosterone (T) on pituitary and serum bioactive and immunoreactive gonadotropins and on gonadotropin hormone subunit messenger RNA levels were compared in the absence of GnRH. Male rats were implanted with pellets of either cholesterol, B or T. At implantation, 2 and 4 days later half of each group received GnRH antagonist and animals were killed 5 days after implantation. As expected, GnRH antagonist lowered bioactive and immunoreactive serum FSH and LH, pituitary FSH, LHβ and FSHβ mRNA. B treatment alone lowered bioactive and immunoreactive serum FSH and immunoreactive serum LH. B reversed the antagonist effect on bioactive and immunoreactive pituitary FSH and FSHβ mRNA. T alone lowered bioactive and immunoreactive serum FSH and LH levels. T reversed the antagonist effect on bioactive and immunoreactive pituitary FSH. T lowered bioactive and immunoreactive pituitary LH and LHβ mRNA and partially reversed the antagonist effect on FSHβ mRNA. The data suggest that either B or T enhance FSH synthesis by acting directly at the gonadotrope, but that B does not affect LH variables to the same extent as T. The results suggest that in stressed animals, when T levels are reduced, B can substitute for T in sustaining FSH synthesis.

Measurement of Urinary Gonadotropins Using Immuno-fluorometric Assay

Urinary luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations were determined by immuno-fluorometric assay (IFMA) and compared with the values determined by immuno-radiometric assay (IRMA). The results of gel chromatography of urine suggested that in IFMA immunoreactive LH consisted of both intact LH and LH β-subunit, while the immunoreactive LH in IRMA was mainly intact LH. In LH measurement, IFMA was much more sensitive than IRMA. Good correlations were observed between urinary gonadotropin concentrations corrected by urinary creatinine in first morning voided urine and mean serum gonadotropin concentrations during the first three hours of sleep.The reference ranges of urinary gonadotropins in school children aged 6-17 were determined, and the change of urinary gonadotropin concentrations according to pubertal development was investigated in normal short children. Urinary LH levels and urinary LH/FSH ratios in IFMA increased 20-fold according to age and were useful in estimating pubertal development.Urinary LH and FSH measurement by IFMA is simple and noninvasive, and therefore will be suitable for investigating gonadotropin secretion in normal and abnormal pubertal development.

Measurement of secretogranin II release from individual adenohypophysial gonadotropes.

Secretogranin II (SG-II) is an acidic 86-kDa protein found in high abundance in the anterior pituitary gland. In the present studies, we investigated the secretion and the localization of SG-II using pituitary cells from female rats at all stages of the estrous cycle. Double immunofluorescence staining revealed that SG-II immunoreactivity was localized in low abundance in about half of all pituitary cells and in high abundance in all of the luteinizing hormone (LH)-immunoreactive cells (which represent approximately 5% of all pituitary cells). Using a reverse hemolytic plaque assay for measurement of SG-II release from individual pituitary cells in culture, we found that SG-II secretion was strongly stimulated by gonadotropin-releasing hormone in a dose-related fashion, and the amount of SG-II secretion was also related to the stage of the estrous cycle: it was highest at proestrus and lowest at estrus. SG-II plaque assay followed by LH immunofluorescence staining further revealed that all the SG-II-secreting cells contained LH immunoreactivity. At proestrus all the LH-immunoreactive cells secreted SG-II, whereas another days of the estrous cycle only a fraction of them did so. Thus our findings demonstrate a striking resemblance between SG-II and LH with regard to cell localization and secretory regulation.

Decreased immunoreactive inhibin and increased FSH levels in cryptorchidism after orchidopexy.

The blood FSH level is often high in patients with severe testicular disorders including cryptorchids. To examine whether inhibin is involved in the increase in FSH we measured immunoreactive inhibin, FSH, LH, and testosterone in 17 patients after orchidopexy. FSH was extremely high (20 mIU/ml or above) in 3 patients. The inhibin level was significantly lower (P < 0.01) in these 3 patients (6.47 +/- 2.19 IU/ml; mean +/- SEM) than in the other 14 patients (14.31 +/- 3.96 IU/ml). All 3 high-FSH patients had azoospermia. Testosterone and LH were normal in one of them. Even considering problems involved in the inhibin assay, the high FSH levels are considered to reflect reductions in the blood inhibin level due to Sertoli cell dysfunction. These findings suggest that inhibin plays an important role in the suppression of FSH at least in some patients after orchidopexy.

Involvement of endogenous opioids in the regulation of LH and testosterone release in the male horse.

To investigate the involvement of endogenous opioids in the regulation of gonadotrophin release in male horses, effects of the opioid antagonist naloxone (0.5 mg kg-1 i.v.) on plasma LH and testosterone concentrations and the possible influence of season and of gonadal steroids were investigated. To determine quantitative as well as qualitative changes in gonadotrophin release, LH concentrations were measured by radioimmunoassay and by an in vitro bioassay. Experiments were performed in May, August and December. In stallions, basal LH secretion in May and August was significantly higher than in December (May versus December: P < 0.01; August versus December: P < 0.05); plasma testosterone concentrations were highest in August (August versus May: P < 0.05, August versus December: P < 0.001). The basal bioactive LH concentration and the ratio of bioactive:immunoreactive LH in stallions were highest in May. Therefore, in addition to seasonal changes in quantitative LH secretion, the bioactivity of LH in the circulation also undergoes seasonal variations. Bioactive LH concentrations and the bioactive:immunoreactive ratio in geldings were higher than in stallions. Naloxone caused a significant increase in LH release in stallions in August and December (P < 0.001); no significant increase was found in May (P = 0.06). In geldings, naloxone did not induce any changes in LH secretion; in stallions, a highly significant correlation was observed between basal testosterone concentrations and the LH increment after injection of naloxone (P < 0.001). In August and December, the bioactive:immunoreactive ratio increased significantly (P < 0.05) after injection of naloxone in stallions, indicating a preferential release of LH molecules with high bioactivity. The bioactive:immunoreactive ratio did not change after naloxone injection in May. The naloxone-induced LH release was followed by a significant increase in plasma testosterone concentrations in stallions in August (P < 0.001) and December (P < 0.05). In conclusion, endogenous opioid systems are involved in the regulation of LH and testosterone secretion in stallions. These mechanisms undergo seasonal changes: their activity is increased during winter and decreased during the breeding season. By affecting LH release, endogenous opioids, at least in part, regulate seasonal changes in reproductive activity in the stallion.

Ovarian stromal hypertrophy in hyperandrogenic women

By using vaginal endosonography, ovarian stromal hypertrophy has been shown to be a strong diagnostic feature of polycystic ovarian syndrome and related states. However, this sign is difficult to quantify and to correlate with other findings because of its subjectivity. We have evaluated the use of computer assisted analysis of ultrasound scans to provide more objective measurements of ovarian structure and size. We used a computer assisted method for the reading of ultrasound scans. It allowed selective calculation of the stromal area by subtraction of the cyst area from the total ovarian area on a longitudinal ovarian section. A consecutive series of 57 patients with hyperandrogenism (group 1), 17 patients with hypothalamic anovulation (group 2) and 20 normal women (group 3). By computerized measure, 75% patients from group 1 had a bilateral stromal area above the mean +2 SD (700 mm2) of women from group 3. All patients from group 2 were below this threshold. Serum LH level was above the normal range in 45% patients from group 1. The stromal area correlated positively with the serum delta 4-androstenedione (r = 0.47, P < 0.005) and 17 alpha-hydroxyprogesterone (r = 0.39, P < 0.005) levels, exclusively in group 1. It did not correlate with the basal serum testosterone, LH or insulin levels. The cyst area did not correlate with any hormonal parameter. Ovarian stromal hypertrophy is a frequent and specific feature of hyperandrogenism. It correlates with the ovarian androgenic dysfunction. Its presence is not always linked with elevated serum immunoreactive LH levels. Further data are needed to elucidate the role of insulin and ovarian growth factors.

Secretion of bioactive and immunoreactive luteinizing hormone in patients with the polycystic ovaries syndrome

Basal secretion of immunoreactive and bioactive LH was measured in 24 patients with polycystic ovaries, secretion during LH-RF test in 18 patients. Basal LH level was assessed from in vitro testosterone secretion by murine Leydigs cells. The content of basal LH and basal LH to FSH ratio in patients with the polycystic ovaries syndrome was markedly increased vs. the norm. Three types of gonadotroph responses were observed in the patients in response to LH-RF, these responses differing by increment rate, time course of secretion, and ratio of secreted basal and immunoreactive LH. Gonadotroph response was found related to ovarian morphology and clinical manifestations of the disease. Administration of LH-RF to patients with polycystic ovaries and tecomatosis changed the ratio of secreted basal and immunoreactive LH by reducing basal LH level. In young girls and women aged under 20 the increment of basal and immunoreactive LH noticeably surpassed its values in older patients with longer disease duration.

Effects of the opioid antagonist naloxone on release of luteinizing hormone in mares during the anovulatory season.

To investigate an involvement of endogenous opioids in the regulation of circannual changes in reproductive activity, effects of the opioid antagonist naloxone on the concentration of immunoreactive and bioactive luteinizing hormone (LH) in plasma were measured in mares during the anovulatory season. Naloxone (0.5 mg/kg i.v.) caused a significant increase (P < 0.05) in immunoreactive as well as bioactive LH concentration in plasma. The amplitude of the increase in LH concentrations measured with an in vitro bioassay was more pronounced than the amplitude of the increase in LH secretion determined by radioimmunoassay. This indicates that although in seasonal anovulatory mares the bioactivity of LH in plasma is low, highly bioactive LH is present in the anterior pituitary and can be released by naloxone. The LH response to naloxone did not depend on the degree of ovarian follicular activity. It can be concluded that a tonic opioid inhibition of LH release is present in mares during at least part of the anovulatory season and that endogenous opioids seem to be involved in the regulation of seasonal reproductive activity in the horse. In contrast to the situation during the breeding season, the opioid systems regulating LH release are activated independently of luteal progesterone.

Age-related changes in the secretion of LH in vivo and in vitro in infantile and prepubertal Holstein bull calves

The objectives of this study were (i) to determine whether age-related changes in the secretion of LH are associated with alterations in secretory activity or numbers of gonadotrophs, and (ii) to determine whether gonadotrophs obtained from the pars distalis and pars tuberalis undergo similar age-related changes in function. Blood samples were collected from Holstein bull calves every 15 min for 12 h at < 1, 12, and 42 weeks of age (n = 5 per age group) to characterize the secretion of LH. Calves were killed 3-5 days later. The pars distalis and pars tuberalis were enzymatically dispersed into suspensions of single cells. Cells from the pars distalis were (i) extracted with 0.01 mol NaHCO3 l-1, (ii) fixed for immunocytochemical analysis, and (iii) cultured in six-well plastic plates at a density of 500,000 cells per well in media containing 2.5% homologous calf serum for 18 and 72 h. Cells from the pars tuberalis were cultured as for pars distalis cells. As expected, LH pulse frequency increased (P < 0.01) between one and 12 weeks of age and then declined. The percentage of cells from the pars distalis containing immunoreactive LH averaged 8.4%, and did not change with age. The mass of the pars distalis and the total number of cells recovered increased with age (P < 0.05); consequently, the number of gonadotrophs recovered also increased. The initial content of LH of pars distalis cells changed with age and was greatest at 12 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of oestrogen treatment on serum gonadotrophin bioactivity, immunoreactivity and isohormone distribution, and on immunoreactive inhibin levels, in prostatic cancer patients

No data are available on effects of long-term exposure to oestrogen on bioactivity of gonadotrophins in men. We studied the effects of a 6-month oestrogen therapy on serum FSH and LH bioactivity (B), immunoreactivity (I) and isohormone distribution, and on serum I-inhibin levels, in patients with prostatic carcinoma. Eleven men with advanced prostatic cancer were studied, each receiving 160 mg of polyoestradiol phosphate (Estradurin) once a month intramuscularly for 6 months. Serum samples were collected before, and after 2 and 6 months of oestrogen treatment. Serum B- and I-FSH levels were measured by immature rat granulosa cell bioassay and immunofluorometric (IFMA, Delfia) assay, respectively, and those of B- and I-LH by mouse interstitial cell bioassay and IFMA, respectively. Serum oestradiol (E2) concentrations were measured by IFMA assay, and serum testosterone (T) and inhibin levels by radioimmunoassay. Isoelectric focusing was used for fractionation of the FSH and LH isoforms. The pretreatment levels of B-FSH and I-FSH were 84.7 +/- 21.6 and 11.4 +/- 3.2 IU/l (mean +/- SEM), respectively, and the B/I ratio of FSH was 8.3 +/- 1.0. The pretreatment levels of B-LH and I-LH were 23.5 +/- 3.2 and 10.1 +/- 2.3 IU/l, respectively, and the B/I ratio was 3.0 +/- 0.4. After 6 months of oestrogen therapy, B-FSH and I-FSH decreased to 37.5 +/- 8.1 (P < 0.05) and 1.3 +/- 0.3 IU/l (P < 0.01), respectively, but the B/I ratio of FSH increased to 28.5 +/- 4.2 (P < 0.05). B- and I-LH levels decreased in 6 months to 7.4 +/- 0.9 and 2.3 +/- 0.5 IU/l (P < 0.01), respectively, but no change was found in the B/I ratio of LH. Serum T levels decreased from 19.0 +/- 2.6 to 2.7 +/- 0.9 nmol/l (P < 0.01) during the 6-month treatment, and the respective E2 levels increased from 0.2 +/- 0.01 to 4.4 +/- 0.5 nmol/l (P < 0.01). Serum I-inhibin levels were analysed from eight patients. The levels at 0, 2 and 6 months were 0.81 +/- 0.09, 0.50 +/- 0.03 and 0.54 +/- 0.01 microgram/l, respectively. Gonadotrophins in the pretreatment and 6-month samples of four patients were analysed by isoelectric focusing. In FSH of all subjects, and in LH of three subjects, a shift from acidic to more basic isoforms occurred after oestrogen therapy. This is in keeping with the increase of the B/I ratio of FSH. With LH, the isoform shift occurred between fractions with similar B/I ratios, and hence there was no shift in the overall B/I ratio. Oestrogen therapy of men suppressed bioactive and immunoreactive levels of gonadotrophins. The B/I ratio of FSH increased, and this increase was associated with a shift in the isohormone profile to more basic forms. In contrast, no change occurred in the B/I ratio of LH, even though changes in the isohormone profile were observed. Hence, not all changes in the isohormone distribution of gonadotrophins result in changes of the intrinsic in-vitro bioactivity.

The hypothalamic-pituitary-ovarian axis in patients with endometriosis is suppressed by leuprolide acetate but not by danazol

To investigate the effects of leuprolide acetate (LA), a GnRH agonist (GnRH-a), and of danazol on the hypothalamic-pituitary-ovarian axis in patients with endometriosis. Ten patients were divided into LA and danazol treatment groups. Serum levels of E2, immunoreactive and bioactive LH, pulsatility of LH, and gonadotropins release by GnRH. Changes in serum E2 levels by hMG administration during LA treatment. Serum E2 level decreased to near castrated levels during the LA treatment, while it remained unchanged during the danazol treatment. Leuprolide acetate administration resulted in a significant suppression of the serum level of bioactive LH, of the pulsatility of LH release, of the pituitary response to GnRH injection, and of the elevation in the serum E2 level by hMG administration, but danazol treatment did not show these suppressive effects. Our results suggest that the hormonal actions of LA and danazol on endometriosis are different from each other, especially in the suppression of serum E2 level.

Differential actions of phospholipase C on gonadotropin-releasing-hormone-stimulated release and glycosylation of luteinizing hormone in rat anterior pituitary cells.

Receptor-mediated activation of phospholipase C (PLC) which releases diacylglycerol and inositol trisphosphate has been implicated in the action of gonadotropin-releasing hormone (GnRH) on gonadotrophs. Previously we demonstrated that the synthetic diacylglycerol, phorbol 12-myristate 13-acetate (PMA) and PLC mimic the stimulatory effects of GnRH on both luteinizing hormone (LH) glycosylation and release. In this study we further investigated how PMA or PLC interact with GnRH to control LH release versus glycosylation. Cultured pituitary cells were incubated in the presence of radiolabeled precursors and GnRH (0, 1, or 100 nM), with or without PMA (10 nM) or PLC (0.24 U/ml) for 4 h. LH translation and glycosylation were monitored by measuring incorporation of [14C]alanine and [3H]glucosamine, respectively, into total (cell and medium) immunoprecipitable LH. Immunoreactive LH (IRLH) was measured by radioimmunoassay. Both PMA and PLC increased (p < 0.01) basal IRLH release, and IRLH release stimulated by 1 nM GnRH. Neither PMA nor PLC exerted an additive effect on IRLH release stimulated by 100 nM GnRH. The interactions between PMA or PLC and GnRH on IRLH release were significant (p < 0.01). Both PMA and PLC elevated (p < 0.01) total [3H]glucosamine-LH, but had no additive effect with 1 nM GnRH; PLC depressed (p < 0.05) the stimulatory effect of 100 nM GnRH, whereas PMA had no effect. The interactions between PMA or PLC and GnRH on LH glycosylation were significant (p < 0.01). PMA, PLC or GnRH alone did not affect total [14C]alanine-LH. In the presence of 1 or 100 nM GnRH, PLC, but not PMA, decreased (p < 0.05) total [14C]alanine-LH.(ABSTRACT TRUNCATED AT 250 WORDS)

Corticosterone in vivo increases pituitary follicle-stimulating hormone (FSH)-beta messenger ribonucleic acid content and serum FSH bioactivity selectively in female rats.

Experimental objectives were to determine: 1) if the native glucocorticoid, corticosterone (B), can selectively increase pituitary FSH and FSH beta messenger RNA (mRNA) in the presence or absence of a GnRH signal; and 2) if B affects the biological activity of the gonadotropins. Metestrous female rats were implanted with cholesterol or B. Each implant group received 100 micrograms GnRH antagonist or control injections every 48 h beginning at the time of implantation, and were killed 5 days later. B significantly increased bioactive serum FSH, with or without GnRH antagonist. GnRH antagonist decreased bioactive serum FSH. Immunoreactive serum FSH was not affected by any treatment. B did not affect bioactive serum LH, but GnRH antagonist significantly suppressed bioactive serum LH. Immunoreactive serum LH was significantly lowered by either B or GnRH antagonist. Neither bioactive nor immunoreactive pituitary FSH or LH content were affected by B, GnRH antagonist, or combined treatments, and no treatment affected alpha or LH beta mRNA. B significantly increased FSH beta mRNA specifically, in the presence or absence of GnRH antagonist. These results demonstrate that corticosterone can increase biological activity of secreted FSH and increase FSH beta mRNA in the absence of a GnRH signal, suggesting a direct effect on the anterior pituitary gland.