Luteinizing Hormone-releasing Hormone Levels Research Articles

MP44-11 GROWTH HORMONE-RELEASING HORMONE (GHRH) ANTAGONISTS REDUCE INFLAMMATION- AND TRANSFORMING GROWTH FACTOR (TGF)-?2-INDUCED PROLIFERATION OF HUMAN BPH-1 PROSTATE EPITHELIAL CELLS GROWN IN 3D CULTURE

You have accessJournal of UrologyBenign Prostatic Hyperplasia: Basic Research & Pathophysiology1 Apr 2016MP44-11 GROWTH HORMONE-RELEASING HORMONE (GHRH) ANTAGONISTS REDUCE INFLAMMATION- AND TRANSFORMING GROWTH FACTOR (TGF)-?2-INDUCED PROLIFERATION OF HUMAN BPH-1 PROSTATE EPITHELIAL CELLS GROWN IN 3D CULTURE Petra Popovics, Andrew V. Schally, Roberto Perez, Rhenzi Cai, and Ferenc G. Rick Petra PopovicsPetra Popovics More articles by this author , Andrew V. SchallyAndrew V. Schally More articles by this author , Roberto PerezRoberto Perez More articles by this author , Rhenzi CaiRhenzi Cai More articles by this author , and Ferenc G. RickFerenc G. Rick More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.267AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Benign prostatic hyperplasia (BPH) is frequently associated with chronic inflammation. Epithelial-to-mesenchymal transition (EMT) has been recently indicated as a major factor in the pathogenesis of BPH. Evidence also suggests that inflammatory cytokines may induce BPH. Hypothalamic neuropeptides, GHRH, luteinizing hormone-releasing hormone (LHRH) and their receptors are expressed in experimental models of BPH in which antagonists of GHRH and LHRH have been shown to suppress the levels of proinflammatory cytokines and alter the expression of genes related to EMT. These findings imply a role of GHRH/LHRH in the development of prostatitis, however, this has not been investigated to date. METHODS Human BPH-1 prostatic cell line was used to generate matrigel-embedded 3D cultures in which average sphere diameters were evaluated. Chronic inflammation was induced by treating cells with THP-1 macrophage-conditioned medium whereas EMT was triggered with TGF-ß1 or TGF-ß2 peptides. The role of secreted LHRH and GHRH in inflammation-induced proliferation was determined by using the LHRH antagonist, degarelix, and a specific GHRH antagonist developed in our lab. The presence of receptors for GHRH and LHRH was confirmed in 3D cultures by immunocytochemistry and quantitative RT-PCR. RESULTS BPH-1-derived spherical structures expressed cell membrane receptors for LHRH and GHRH. Macrophage-conditioned medium induced a 26% increase (P<0.001) in the average diameter of cells and a 2-fold elevation in the expression of the EMT markers N-cadherin (p<0.01) and Snail (p<0.001) as detected by qPCR. The expression of GHRH was also increased 2.7-fold (p<0.001), whereas mRNA levels of LHRH were slightly reduced (ns). GHRH antagonist reduced inflammation-induced increase in diameter by 64% (P<0.01), while no significant change was observed after degarelix treatment. TGF-ß2 increased average sphere diameter by 32%, but this effect was reduced by 67% by the GHRH antagonist (P<0.001). In contrast, TGF-ß1 did not significantly affect sphere diameter. CONCLUSIONS This study identifies GHRH as an important factor in inflammation-induced proliferation and TGF-ß2-triggered EMT of prostate epithelial cells and suggests the merit of further investigation to elucidate the effects of GHRH antagonists in the reduction of inflammation-induced BPH. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e602-e603 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Petra Popovics More articles by this author Andrew V. Schally More articles by this author Roberto Perez More articles by this author Rhenzi Cai More articles by this author Ferenc G. Rick More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Establishment and clinical application of enzyme immunoassays for determination of luteinizing hormone releasing hormone and metastin

Metastin, a 54-residue peptide, was identified as the cognate ligand of human G-protein-coupled receptor GPR54. Since metastin is a gene product of the human metastasis suppressor gene 'KiSS-1', early studies on metastin were focused on its activity as a tumor metastasis suppressor. Recently, there have been some reports that metastin is found in human plasma and is particularly abundant in the plasma of pregnant women. Dysfunction of the GPR54 receptor causes diseases that are characterized by an insufficient release of gonadotropin and lack or delay of pubertal maturation. This information strongly suggests that metastin is involved in the regulation of reproductive endocrine functions. In order to determine the plasma levels of metastin and luteinizing hormone releasing hormone (LHRH) in an isolated hypogonadotropic hypogonadism (IHH) patient, who received intermittent administrations of LHRH, we tried to establish a sensitive and specific enzyme immunoassay. The plasma LHRH levels of the patient were very high, while plasma metastin levels were at almost the same levels as circadian rhythms of healthy male humans. In the central nervous system, metastin stimulates the neuroendocrine reproductive axis. However, the effects of peripheral metastin are not known. Our result suggested that peripheral metastin had a genesis and activity different from central metastin.

An increase in in vivo release of LHRH and precocious puberty by posterior hypothalamic lesions in female rhesus monkeys (Macaca mulatta)

We have previously shown that a decrease in gamma-aminobutyric acid (GABA) tone and a subsequent increase in glutamatergic tone occur in association with the pubertal increase in luteinizing hormone releasing hormone (LHRH) release in primates. To further determine the causal relationship between developmental changes in GABA and glutamate levels and the pubertal increase in LHRH release, we examined monkeys with precocious puberty induced by lesions in the posterior hypothalamus (PH). Six prepubertal female rhesus monkeys (17.4 +/- 0.1 mo of age) received lesions in the PH, three prepubertal females (17.5 +/- 0.1 mo) received sham lesions, and two females received no treatments. LHRH, GABA, and glutamate levels in the stalk-median eminence before and after lesions were assessed over two 6-h periods (0600-1200 and 1800-2400) using push-pull perfusion. Monkeys with PH lesions exhibited external signs of precocious puberty, including significantly earlier menarche in PH lesion animals (18.8 +/- 0.2 mo) than in sham/controls (25.5 +/- 0.9 mo, P<0.001). Moreover, PH lesion animals had elevated LHRH levels and higher evening glutamate levels after lesions, whereas LHRH changes did not occur in sham/controls until later. Changes in GABA release were not discernible, since evening GABA levels already deceased at 18-20 mo of age in both groups and morning levels remained at the prepubertal levels. The age of first ovulation in both groups did not differ. Collectively, PH lesions may not be a good tool to investigate the mechanism of puberty, and, taking into account the recent findings on the role of kisspeptins, the mechanism of the puberty onset in primates is more complex than we initially anticipated.

Hypothalamic Control of Mitogen-Induced Proliferative Responses and Luteinizing Hormone-Releasing Hormone Levels in Thymus and Peripheral Blood of Rat Fetuses

The role of endogenous luteinizing hormone-releasing hormone (LHRH) in the development of concanavalin A (ConA)-induced proliferative responses was studied in rat fetuses. Preliminary treatment of fetuses in utero with either the LHRH receptor antagonist or anti-LHRH antibodies resulted in the suppression of ConA-induced proliferative responses of thymocytes. LHRH and LHRH-immunopositive cells, morphologically similar to thymocytes, were detected in intact fetal thymus. A significant content of LHRH was also found in the peripheral blood of fetuses. The LHRH content in thymus and plasma was similar in males and females. Surgical ablation of the hypothalamus resulted in 2-fold decreases in thymus and plasma levels of LHRH in 21-day-old fetuses compared to sham-operated fetuses. It was concluded that LHRH regulates mitogen-induced proliferative responses of thymocytes during prenatal ontogenesis in the rat. The main source of plasma LHRH at that period is the hypothalamus. Moreover, LHRH is synthesized in the fetal thymus. Thus, LHRH is suggested to have not only a central effect but also to be involved in autocrine or paracrine regulation of proliferative immune responses.

Central administration of an antisense oligodeoxynucleotide against type I pituitary adenylate cyclase-activating polypeptide receptor suppresses synthetic activities of LHRH-LH axis during the pubertal process

In the present study, we determined the expression of pituitary adenylate cyclase-activating polypeptide (PACAP) and PACAP receptor type I (PAC 1) genes during juvenile development and the pubertal process. Female rats were assigned — based on uterine weights, the presence and abundance of uterine fluid, and their vaginal patency — to one of the following: anestrus (AE), early proestrus (EP), late proestrus (LP) or first estrus (E). The hypothalami from 22-, 24- and 26-day-old animals and from those in the peripubertal phases of AE, EP, LP and E were collected, and the content of PACAP and PAC 1 mRNA was assessed. These levels were found to decrease in EP and LP. To determine the effect of PACAP on prepubertal luteinizing hormone-releasing hormone (LHRH) and LH synthesis through PAC 1, a PAC 1 antisense oligodeoxynucleotide (ODN) was i.c.v.-administered, and mRNA levels of LHRH, LH β, and LHRH receptor (LHRH-R) were determined. Prepubertal increases in LHRH, LH β, and LHRH-R mRNA levels were markedly suppressed, and the onset of puberty was delayed by the i.c.v. injection of the antisense PAC 1 ODN. These data suggest that PACAP may play a role in the regulation of hypothalamic LHRH neurons, through which it regulates synthetic machinery of pituitary LH, during the pubertal process.

An increase in glutamate release follows a decrease in gamma aminobutyric acid and the pubertal increase in luteinizing hormone releasing hormone release in the female rhesus monkeys.

Previously we have shown that release of gamma-aminobutyric acid (GABA) in the stalk-median eminence (S-ME) is high in prepubertal monkeys and that a decrease in GABA release triggers the onset of puberty. However, it is still unclear how disinhibition of the luteinizing hormone releasing hormone (LHRH) neuronal system from GABA input is followed (or accompanied) by an increase in stimulatory signals, such as glutamatergic input to LHRH neurons. To clarify the temporal relationship between the reduction of the GABAergic inhibitory signal and the enhancement of the glutamatergic stimulatory signal in the control of LHRH release at the onset of puberty, we conducted two experiments using a push-pull perfusion method. In the first experiment, we measured developmental changes in release of LHRH, GABA, and glutamate in the S-ME. LHRH levels were very low in prepubertal monkeys, increased to higher levels in early pubertal monkeys, with the highest LHRH levels occurring in mid-pubertal monkeys. As we previously observed, GABA levels were high in prepubertal monkeys and then decreased in early- and mid-pubertal monkeys. In contrast, glutamate levels were very low in prepubertal monkeys, increased dramatically in early pubertal monkeys, and then slightly decreased in mid-pubertal monkeys, although mid-pubertal levels remained much higher than prepubertal levels. In the second experiment, we measured GABA, glutamate and LHRH in the same samples obtained from prepubertal monkeys which were infused with an antisense oligodeoxynucleotide (AS) for glutamic acid decarboxylase (GAD) 67 mRNA into the S-ME. GAD67 is a catalytic enzyme for GABA synthesis from glutamate, and AS GAD67 mRNA interferes with GAD67 synthesis. Infusion of the AS GAD67 induced a decrease in GABA release, which subsequently resulted in an increase in LHRH release. Surprisingly, glutamate release also increased several hours after the decrease in GABA release, and the increased LHRH release continued. These data are interpreted to mean that a decrease in GABA synthesis by interference with GAD67 synthesis and the reduction of GABA release in the S-ME trigger an increase in LHRH release, but that a subsequent increase in glutamate release in the S-ME further contributes to the pubertal increase in LHRH release at the onset of puberty. The data further support our hypothesis that GAD plays an important role in the mechanism of the onset of puberty.

Ethanol‐Induced Alterations in the Posttranslational Processing, But Not Secretion of Luteinizing Hormone‐Releasing Hormone In Vitro

The effects of ethanol (EtOH) on the male hypothalamic pituitary reproductive axis are multiple and varied. Although direct gonadal toxicity has been reported, hypothalamic-pituitary perturbations have also been noted. The difficulty of sampling the hypothalamus has made direct investigation of EtOH-induced alterations on luteinizing hormone-releasing hormone (LHRH) fraught with interpretation problems. To circumvent this, we have conducted a series of experiments exploring the effect of 200 mg% EtOH in vitro on GT1-7 cells, a newly developed LHRH secreting neural cell line. Cell lines were treated with EtOH-containing or EtOH-free media for 2, 6, 24, or 48 hr. EtOH caused no significant change in LHRH secretion at any time point, although there was a trend to increased secretion after 2 hr EtOH exposure when compared with control. Significantly increased total (i.e., cellular plus secreted) pro-LHRH coupled with significantly reduced cellular LHRH after 6 hr only of EtOH exposure suggested that EtOH caused a transient decrease in processing from bioinactive pro-LHRH to bioactive LHRH. However, even at this time point, LHRH secretion from these EtOH-exposed cells was no different than from control cells. Steady-state LHRH mRNA levels were not changed by EtOH at any time point. These findings are concordant with previous in vitro data using hypothalamic tissue that has similarly demonstrated no effect of EtOH on LHRH secretion. Taken together with the in vivo demonstration that EtOH reduces hypothalamic-pituitary portal blood levels of LHRH, these data indicate that EtOH exerts its effect either at an extrahypothalamic locus and/or on non-LHRH-producing cells within the hypothalamus.

The effect of castration on steady state levels of luteinizing hormone-releasing hormone (LHRH) mRNA and proLHRH processing: time course study utilizing semi-quantitative reverse transcription/polymerase chain reaction.

Many studies have consistently shown that castration induces a prompt increase in serum levels and pituitary content of the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as a concomitant rise in steady state levels of the messenger RNAs directing their synthesis. The reports of effects of castration on the overall physiology of hypothalamic luteinizing hormone-releasing hormone (LHRH)--steady state levels of LHRH mRNA, post-translational processing and secretion--have, however, not been consistent. The goal of the studies reported here was to provide the first analysis of the effect of castration, at multiple postoperative time points, on steady state levels of LHRH mRNA and on the levels of hypothalamic proLHRH. All these data are correlated with hypothalamic levels of the mature LHRH decapeptide and with serum and pituitary levels of immunoreactive LH and FSH. Adult male rats were either castrated or sham-castrated (controls) and then sacrificed at 1, 3, 5, 7, 14, 21 or 28 days postoperatively. As expected, there was a prompt and sustained rise in serum immunoreactive LH and FSH in castrates compared with sham-operated animals. Intra-pituitary LH levels rose above levels in the sham-operated animals by 14 days post castration. Intra-pituitary FSH showed a biphasic response, first falling significantly below control levels, then rising above control levels at 21 days. Steady state levels of LHRH mRNA in castrates, measured by reverse transcription/polymerase chain reaction, were increased about 2-fold above control levels by 1 day postoperatively, but were virtually identical to control levels at each of the other time points despite marked changes in the gonadotropins. ProLHRH content in castrates was 1.8-times that seen in controls at 1 day post castration (P<0.05), concomitant with the rise in steady state levels of LHRH mRNA at that time point. However, proLHRH content in castrates was no different from that seen in controls at each of the later time points examined. LHRH content was unchanged through 7 days after castration, but then fell significantly to 57% of control levels in hypothalami from animals gonadectomized 14 to 21 days previously (P<0.001 vs control), and to 54% of sham-operated levels at 28 days postoperatively (P<0.001). We conclude that: (1) changes in steady state levels of LHRH mRNA after castration are small and transient and (2) increased proLHRH coupled with unchanged LHRH levels at 1 day post castration, and castrate animal proLHRH at control levels coupled with falling LHRH at later post-castration time points indicate that the effect of gonadectomy on post-translational processing of proLHRH to LHRH is, likewise, small and transient. In aggregate our data suggest that most of the increase in serum LH and FSH seen in male rats after castration is not mediated at the hypothalamic level.

Thymus influences liver functions through hypothalamus-pituitary-gonad axis in rats

The aim of the review is to summarize our recent studies on the influence of the thymus on liver functions and its intermediary pathway in rats. Young adult thymectomized rats were used as a model in the experiments, and either thymic peptides or sex hormones were supplemented to these animals. Liver microsomal cytochrome P-450 and aminopyrine-N-demethylase (ADM) activities were decreased in thymectomized rats, and the change in the male was more significant than that in female rats. An increase of liver malondialdehyde (MDA) and a decrease of liver glutathione (GSH) and superoxide dismutase activity were observed in the female thymectomized rats, but not in the males. Accompanied by the increase of MDA, a decline of membrane fluidity of liver microsomes and mitochondria and a decrease of Ca 2+ uptake by liver microsomes were exhibited in the female thymectomized rats. Subcutaneous injection of thymic peptides decreased MDA level, and increased GSH content, membrane fluidity and Ca 2+ uptake by microsomes in the liver of thymectomized rats. On the other hand, male thymectomized rats showed a decrease of hypothalamic luteinizing hormone-releasing hormone (LHRH), plasma luteinizing hormone (LH) and testosterone levels. Subcutaneous injection of testosterone propionate to these animals restored their liver P-450 and ADM activities to normal levels. Female thymectomized rats exhibited a decline of hypothalamic LHRH and plasma estradiol levels. Supplementation of estradiol benzoate reversed the increase of liver MDA in these animals. The data suggest that the thymus may influence liver functions through the hypothalamus-pituitary-gonad axis. Thus, a new ‘thymus-neuroendocrine-liver pathway’ is proposed, which may account for the significance of the thymus in maintaining homeostasis and integrative functions in the body.

Signal Requirements for Production of Luteinizing Hormone Releasing-Hormone by Human T Cells

We have previously demonstrated that both human CD4+ and CD8+ T lymphocytes produce enhanced levels of luteinizing hormone-releasing hormone (LHRH) mRNA and peptide upon stimulation with monoclonal antibody directed at the CD3 component of the T cell receptor for antigen (TCR) or mitogenic lectin. In the current study, we define the signaling pathways that control TCR-mediated LHRH production by using agents known to affect distinct signals, and compare the messenger systems required for LHRH response to other T-cell-associated activation responses, such as expression of CD69 and interleukin-2 receptor (IL-2R) molecules and production of interleukin-2 (IL-2). Results indicate that the activation of protein kinase C (PKC) is essential for LHRH production by previously nonstimulated T cells, not increased concentration of cytosolic-free calcium ([Ca]2+]1). Phorbol ester (PMA), a direct activator of PKC, provoked LHRH production and cell surface expression of CD69 and IL-2R molecules by T cells, but not IL-2 synthesis. The synthesis of IL-2 by T cells required costimulation with PMA and ionomycin, a Ca2+ ionophore. Consistent with these observations, H7, an inhibitor of PKC, prevented T cells from producing LHRH upon activation with mitogen. However, LHRH production was not suppressed by HA 1004, which inhibits all cyclic nucleotide-dependent protein kinases except for PKC. Genistein, a selective inhibitor of protein tyrosine kinase, blocked PMA-induced increase in LHRH production, but not CD69 and IL-2R expression, suggesting that protein tyrosine phosphorylation events distal from PKC activation may play a role in regulating LHRH response.

Immortalized hypothalamic luteinizing hormone-releasing hormone (LHRH) neurons: a new tool for dissecting the molecular and cellular basis of LHRH physiology.

1. Two LHRH neuronal cell lines were developed by targeted tumorigenesis of LHRH neurons in vivo. These cell lines (GN and GT-1 cells) represent a homogeneous population of neurons. GT-1 cells have been further subcloned to produce the GT1-1, GT1-3, and GT1-7 cell lines. While considerable information is accumulating about GT-1 cells, very little is currently known about the characteristics and responses of GN cells. 2. By both morphological and biochemical criteria, GT-1 cells are clearly neurons. All GT-1 cells immunostain for LHRH and the levels of prohormone, peptide intermediates, and LHRH in the cells and medium are relatively high. 3. GT-1 cells biosynthesize, process, and secrete LHRH. Processing of pro-LHRH appears to be very similar to that reported for LHRH neurons in vivo. At least four enzymes may be involved in processing the prohormone to LHRH. 4. LHRH neurons are unique among the neurons of the central nervous system because they arise from the olfactory placode and grow back into the preoptic-anterior hypothalamic region of the brain. Once these neurons reach this location, they send their axons to the median eminence. With respect to the immortalized neurons, GN cells were arrested during their transit to the brain. In contrast, GT-1 cells were able to migrate to the preoptic-anterior hypothalamic region but were unable correctly to target their axons to the median eminence. These problems in migration and targeting appear to be due to expression of the simian virus T-antigen. 5. While GT-1 cells are a homogeneous population of neurons, they are amenable to coculture with other types of cells. Coculture experiments currently under way should help not only to reveal some of the molecular and cellular cues that are important for neuronal migration and axonal targeting, but they should also highlight the nature of the cellular interactions which normally occur in situ. 6. GT-1 cells spontaneously secrete LHRH in a pulsatile manner. The interpulse interval for LHRH from these cells is almost identical to that reported for release of LH and LHRH in vivo. GT-1 cells are interconnected by both gap junctions and synapses. The coordination and synchronization of secretion from these cells could occur through these interconnections, by feedback from LHRH itself, and/or by several different compounds that are secreted by these cells. One such compound is nitric oxide. 7. GT-1 cells have Na+, K+, Ca2+, and Cl- channels.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of chronic DDC treatment on LHRH and substance P amidation processes in the rat

We examined the effects of chronic diethyldithiocarbamate (DDC) treatment on the concentrations of methionine-enkephalin, mature and unamidated forms (-Gly) of luteinizing hormone releasing hormone (LHRH) and substance P (SP) in various regions of the central nervous system (CNS). Chronic DDC treatment resulted in elevations of LHRH-Gly like immunoreactivity in the preoptic area (POA) and the medial basal hypothalamus (MBH), as well as elevations in SP-Gly like immunoreactivity in all areas of the CNS examined. Castration altered the ratios of SP-G-like/SP-like immunoreactivity in the pons, and LHRH-Gly like immunoreactivity in the MBH. Met-enkephalin concentrations were significantly elevated in the pons and medulla of intact DDC-treated animals, and in the POA of both intact- and castrated DDC-treated animals. Results demonstrate that it is possible to detect basal levels of unamidated LHRH and SP in many areas of the CNS, with ratios of unamidated/amidated peptides representing a unique and sensitive method for determining altered posttranslational processing of these transmitters, especially under altered endocrine states such as castration. Pharmacological blockade of terminal enzymatic processing of these peptides may be useful in studying upstream regulatory events in peptidergic neurons.

Relationship between neuropeptide Y and luteinizing-hormone-releasing hormone immunoreactivities in the hypothalamus and preoptic region.

The purpose of this study was to examine the anatomical relationships of perikarya and fibers containing neuropeptide Y (NPY) and luteinizing-hormone-releasing hormone (LHRH) in the hypothalamus and preoptic region of female rats. In view of our previous report of stimulatory effects of estrogen on LHRH and NPY levels in the median eminence, animals were bilaterally ovariectomized and subsequently implanted subcutaneously with capsules containing estradiol benzoate in oil or vehicle. Following intracerebroventricular injection of colchicine, rats were perfused with fixative and their brains sectioned and processed for immunohistochemical visualization of NPY and LHRH in the same section and in consecutive sections. Estrogen treatment had no discernible effect on the distribution or relationship of these peptides. NPY-immunoreactive fibers were intimately associated with LHRH-labeled primary dendrites and perikarya in the medial preoptic region and horizontal limb of the diagonal band of Broca. Fibers containing NPY or LHRH overlapped extensively in the lateral palisade region of the median eminence and also in the subependymal and internal zones. The external zone of the median eminence displayed relatively less overlap of these peptide systems. LHRH-immunoreactive axons coursed among NPY-labeled perikarya in the arcuate nucleus and appeared to contact these cells. These results suggest that NPY-containing axons may influence LHRH-positive neurons at the cell body and also at the site of axon termination in the median eminence. LHRH-containing axons appear to contact NPY-immunoreactive perikarya in the arcuate nucleus and may interact with terminals in the median eminence. This arrangement may provide a mechanism for communication between NPY and LHRH neurons and for the neuroendocrine coordination of hypothalamic NPY and LHRH secretion before ovulation.

Enzyme-linked immunosorbent assay (ELISA) for luteinizing hormone releasing hormone (LH-RH) using a heterobifunctional cross-linking agent, N-[beta-(4-diazophenyl)ethyl]maleimide.

Luteinizing hormone-releasing hormone (LH-RH) was first labeled with an enzyme, beta-D-galactosidase (beta-Gal; EC 3.2.1.23), using N-[beta-(4-diazophenyl)ethyl]maleimide (DPEM) as a heterobifunctional cross-linking agent. An antigen was similarly prepared by coupling LH-RH to mercaptosuccinylated bovine serum albumin with DPEM and was used for the immunization of rabbits for antibodies against LH-RH. A new, simple enzyme-linked immunosorbent assay (ELISA) for LH-RH was developed by using the principle of direct competition between LH-RH and beta-Gal-labeled LH-RH for anti-LH-RH IgG which had been adsorbed to the plastic surface of microtiter plates. LH-RH concentrations lower than 50 pg/assay well were measurable reproducibly by the ELISA, the sensitivity of which was found to be about 6250 times greater than the corresponding high performance liquid chromatography (HPLC) procedure. The specificity of this ELISA seems to be primarily toward the C-terminal region of LH-RH, showing a cross-reaction with the LH-RH6-10 fragment to the same extent as with LH-RH, but no cross-reaction with the LH-RH1-3 and LH-RH4-6 fragments. Using this assay, LH-RH levels were easily measured in the blood and urine of rats following the administration of LH-RH in a single dose of 0.5 mg/kg i.v. The present, newly developed ELISA is a nonradioactive, inexpensive and rapid method, and might be useful for elucidating experimental hypothalamic-pituitary-gonad interactions.

Presence of high concentrations of LHRH in human follicular fluid

Health workers took plasma and human follicular fluid samples from 7 women with uterine fibroids at the First Affiliated Hospital in Heilongijiam China to determine whether luteinizing hormone releasing hormone (LHRH) is in human follicular fluid (HFF) and if it is in HFF what is the relationship between its presence in HFF and in plasma. Laboratory personnel used the LHRH specific radioimmunoassay kit by Immuno Technology Service Production B.V. to detect LHRH concentration in HFf and in plasma. Not only was LHRH present in HFf but its mean concentration was significantly greater than it was in plasma (369.3 pg/ml vs. 29.1 mg/ml; p<.05). LHRH levels in HFF ranged from 99 to 600 pg/ml and in plasma from 13 to 72 pg/ml. Since the LHRH in HFF and in the plasma did not cross-react with the LHRH-like protein in the kit the researchers determined that the LHRH in HFF was not an LHRH-like protein. They proposed 2 possible reasons for the LHRH in HFF to be higher than that in plasma. Certain cells in the human ovary may synthesize and secrete LHRH or the LHRH derives from the plasma where it concentrates in the HFF. They believed the 1st proposed reason to be the most likely reason. Nevertheless they suggested that researchers conduct more detailed tests to determine the origin of LHRH in HFF.

A selective sexually dimorphic response in the median eminence neuropeptide Y

Recent studies show that neuropeptide Y (NPY) is widely distributed in the hypothalamus and that it stimulates luteinizing hormone-releasing hormone (LHRH) release from the medial basal hypothalamus (MBH) of male and female rats. The neuroendorcrine factors that regulate NPY neurosecretion in two sexes are not well understood. We have previously observed that orchidectomy (orch) in male rats decreased and testosterone (T) replacement increased NPY levels selectively in the median eminence (ME), arcuate nucleus (ARC) and ventromedial nucleus (VMN) and the KCl-evoked in vitro release of NPY from the MBH was likewise decreased after orch and restored by testosterone replacement. Now we report that these NPY responses are different in female rats following removal of the ovaries. Ovariectomy (ovx) decreased NPY concentrations in the ARC and VMN and not in the ME. Estrogen replacement restored NPY concentrations in the ARC and VMN, however, in the ME NPY concentration decreased significantly. Further, the KCl-evoked NPY release in vitro from either the MBH or ME of intact and ovx rats was similar. In an additional concurrent comparative study in male and female rats, we observed that of the 6 microdissected hypothalamic sites, NPY levels were approximately 50% less in the ME of intact females than in those of intact male rats. Again, in male rats there was a significant decrease in NPY levels in the ME, ARC and VMN after orch, whereas in female rats, NPY levels in the ARC and VMN, but not in the ME decreased after ovx. When the effects on LHRH levels in the ME were evaluated, we observed that unlike the case of ME NPY, LHRH levels decrease in the ME of both sexes in response to gonadectomy. These studies show that despite the widespread distribution and common source of hypothalamic NPY in male and female rats, a sexually dimorphic NPY response is apparent, selectively, in the ME where NPY levels are lower in females than in males and gonadectomy and appropriate steroid-replacement differentially affects NPY levels and release. In view of the observation that the sexually dimorphic response was seen in the ME NPY and not in ME LHRH, and NPY is an important excitatory signal to LHRH neurons in steroid-treated rats, we speculate that the different pattern of gonadotropin secretion seen in male and female rats may be due, in part, to disparate modes of NPY neurosecretion imposed by postnatal androgenization.

Effects of angiotensin II on LHRH release, as measured by in vivo microdialysis of the anterior pituitary gland of conscious female rats.

The present experiments assessed the effects of central administration of angiotensin II (Ang II) on mean levels of luteinizing hormone-releasing hormone (LHRH) in the extracellular fluid of the anterior pituitary gland, monitored by in vivo microdialysis. Ovariectomized rats were tested under two conditions: (1) nonhormone-treated where Ang II infusion inhibits luteinizing hormone (LH) release, and (2) ovarian hormone-treated where Ang II stimulates LH secretion. Animals were ovariectomized and chronic guide cannulae were implanted, one into the lateral cerebral ventricle for infusion of Ang II and one directed toward the anterior pituitary gland for the insertion of the microdialysis probe. Approximately 1 week later, the dialysis probe was inserted and cemented into place. The length of the dialysis probe transected the pituitary gland from its dorsal to ventral aspects. Dialysis samples were collected at 15-min intervals. Levels of LHRH were continuously monitored in nonhormone-treated animals, prior to and during intracerebroventricular (i.c.v.) infusion of Ang II. The dialysis probe was removed at the end of the experiment. One week later, the same animals were treated with estrogen and progesterone and dialysis of the anterior pituitary gland was performed 3 days later using a protocol identical to the first dialysis sampling session. A separate group of animals was tested to confirm the effects of lateral ventricle infusion of this dose of Ang II on LH release. There were no detectable values of LHRH in dialysis samples from non-hormone-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypothalamic luteinizing hormone-releasing hormone content and serum luteinizing hormone levels in male rats during wallerian degeneration of sympathetic nerve terminals after superior cervical ganglionectomy

The main hypothesis of this study was that sympathetic neurons located at the superior cervical ganglia (SCG) control luteinizing hormone (LH) releasing mechanisms by acting at a hypothalamic site. To test this, medial basal hypothalamus (MBH) luteinizing hormone-releasing hormone (LHRH) content and serum LH levels were measured in male rats subjected to superior cervical ganglionectomy (SCGx) or sham-operation 14 or 38 h earlier, at the time of degeneration of nerve endings post-SCGx. Significantly augmented MBH LHRH levels and decreased circulating LH were found in SCGx rats. In animals subjected to SCGx 14 h earlier and receiving a single injection of the alpha 1-adrenergic blocker prazosin, the beta-adrenergic blocker propranolol or a mixture of both drugs 45 min before sacrifice, only the injection of prazosin prevented the decrease of plasma LH levels. Neither treatment prevented the increase in MBH LHRH content. When prazosin was given every hour starting from the 10th to the 13th h after surgery, it was effective to prevent both the increase of MBH LHRH content and the decrease of serum LH found during sympathetic nerve degeneration. Similar repetitive injections of propranolol resulted in the greatest depression of serum LH, and in the greatest increase of MBH LHRH observed. Serum LH response to LHRH injection was similar in SCGx and sham-operated rats. The data indicate that SCG neurons exert, through inhibitory alpha 1-, and weaker, stimulatory beta-adrenoceptors, a significant influence on LHRH release at a supra-hypophysial site.

Regulation of hypothalamic luteinizing hormone-releasing hormone levels by testosterone and estradiol in male rhesus monkeys

Castration of rhesus monkeys produces hypersecretion of pituitary luteinizing hormone (LH) and a marked reduction in hypothalamic luteinizing hormone-releasing hormone (LH-RH) content. We performed the present study to determine whether treatment with gonadal steroids would reverse the effect of castration by increasing LH-RH content. We found that, when administered in doses that suppressed serum LH, both testosterone (T) and estradiol (E) significantly increased LH-RH in the infundibular nucleus/median eminence. The LH-RH content of 8 other regions, some known to contain LH-RH neurons, was not significantly affected. Thus, gonadal steroids act within a discrete region of the basal hypothalamus to modify LH-RH content. The finding that both T and E were effective in male monkeys supports the hypothesis that aromatization is involved in the negative feedback mechanism.

Hypothalamic Luteinizing Hormone-Releasing Hormone(LHRH) and LH Secretion in Aging Female Rats.

Age-related changes in hypothalamic luteinizing hormone-releasing hormone (LHRH) and luteinizing hormone (LH) secretion were studied in young (6 months), middle-aged (12 months) and old (18 months) female rats. The LHRH levels in the mid-hypothalamic area were higher in intact middle-aged and old females than in young ones. Additionally, there was no age difference in the hypothalamic LHRH levels in male rats. In order to clarify the significance of this age-related increase in female rats, we examined the effects of progesterone treatment in estrogen-primed ovariectomized young and old rats on the LHRH levels in the median eminence (ME) and on plasma LH levels. We found phasic changes in ME-LHRH and plasma LH levels in estrogen-primed rats following progesterone treatment in rats of both ages, but the progesterone-induced change in ME-LHRH levels tended to be delayed in old rats compared with young females. This delay may correspond to the delayed onset, slow and low magnitude of plasma LH increase in old females. The ME-LHRH levels were generally higher in old rats than in young rats. Nevertheless, we found that the increase in plasma LH in response to progesterone treatment in estrogen-primed ovariectomized females was smaller in old rats than young rats. These results suggest that the LHRH secretory mechanism changes with age in female rats. Such alterations may result in the accumulation of LHRH in the mid-hypothalamic area and an increase in ME-LHRH.