Mammalian Gonadotropin-releasing Hormone Research Articles

Active immunization with recombinant GnRH6-CRM197 inhibits reproductive function of male rats

Gonadotropin-releasing hormone (GnRH) vaccines have been successfully used for the inhibition of gonadal development and function, but current GnRH-based vaccines often present variability in the response. Cross-reactive material 197 (CRM197) has been used as carrier molecules to enhance an immune response to associated antigens. So, the synthetic mammalian tandem-repeated GnRH hexamer (GnRH6) gene was integrated into the expression plasmid pET-21a. Recombinant GnRH6-CRM197 protein was subsequently overexpressed in Escherichia coli strain BL21 and purified through Nickel column affinity chromatography and the antigenicity and biological effects of GnRH6-CRM197 were evaluated in rats. Sixteen 4-month-old adult male rats were randomly divided into two groups: the GnRH6-CRM197 group (n = 8) and the control group (n = 8). The GnRH6-CRM197 group rats were subcutaneously immunized with 100 μg of GnRH6-CRM197, administered thrice at 2-week intervals with GnRH6-CRM197.The control group received only a white oil adjuvant. Following the initial immunization, the weights of animals were recorded, and blood samples were collected from the orbital sinus at 4, 4.5, 5, 5.5, 6, 6.5, and 7 months. Serum antibody titers and testosterone concentrations were quantified using ELISA and CLIA, respectively. Additionally, testicular tissues were collected for morphological examination. The results revealed a significant increase in serum GnRH antibody titers (p < 0.05), but a significant decrease in serum testosterone concentrations (p < 0.05), and the weight, length, width, and girth of the testis, and the number of spermatogonia cells, spermatocytes, and sperm cells in the immunized rats. Furthermore, seminiferous tubules revealed significant atrophy and no sperm were observed in the immunized animals. Thus, GnRH6-CRM197 may be an effective antigen and a potential immunocastration vaccine.

Optimizing the gonadoliberin dosage and evaluating the egg quality in the preseason and seasonal artificial reproduction of pond-reared sterlet Acipenser ruthenus

Sterlet Acipenser ruthenus is the smallest in size, early maturing, yet third in production scale among the sturgeon species and as such presents a good model to study reproductive biology. The present study aimed to evaluate the effects of preseason artificial reproduction and reduction of hormonal dosage on the egg quality in pond-reared sterlet. Therefore, a series of three trials were conducted in the period 2021 and 2022 (21 and 22) that evaluated three dosages of mammalian gonadotropin releasing hormone analog des-Gly10-(d-Ala6)-GnRH (40, 20, and 10 µg/kg) in both preseason (January) and seasonal (April) spawning batches (PRE and SEA). The greatest embryo survival was achieved in SEA-21-10 (84.8 ± 5.8 %) and the lowest in PRE-21-40 (31.0 ± 40.7 %). Overall results indicated that a dosage of 10 µg/kg leads to the highest embryo survival. Considering the season, latency time was significantly longer in preseason reproduction being on average about 6 h prolonged (35.1 ± 2.8 h vs. 41.4 ± 2.9 h) and it directly affected the embryo survival (linear correlation r = − 0.769, P = 0.003). Likewise, preseason reproduction yields more variable egg quality, due to impaired performance of later ovulating fish most likely due to lower oocyte maturation competence. The present study found expected latency time at 14 °C to be 37–41 h in the preseason and 31–41 h in season, while the recommended dosage is 10 µg/kg des-Gly10-(d-Ala6)-GnRH. Future studies should develop in vitro tools to evaluate the oocyte maturational competence to improve the egg quality in the preseason.

Spawning Performance and Sex Steroid Levels in Female Pikeperch Sander lucioperca Treated with Poly(lactic-co-glycolic acid) Microparticles.

Simple SummaryPikeperch Sander lucioperca is a promising candidate for intensive aquaculture. However, controlled reproduction has become the major bottleneck in pikeperch production. To improve and optimize its artificial reproduction, an effective method for hormone treatment is needed. The use of a poly(lactic-co-glycolic acid) microparticle-sustained-release system to administer gonadotropin-releasing hormone agonist to pikeperch resulted in acceptable reproductive output. Our results establish the potential of poly(lactic-co-glycolic acid) microparticle as a novel tool for hormone treatment in fish.Pikeperch Sander lucioperca is a piscivorous species considered a promising candidate for the diversification of intensive aquaculture. This study aimed to determine the effect of a sustained-release delivery system incorporating mammalian gonadotropin-releasing hormone agonist (mGnRHa) into poly(lactic-co-glycolic acid) (PLGA) microparticles on the sex steroid levels and aspects of artificial reproduction of pikeperch. Fish were divided into four groups and injected with 20 µg mGnRHa/kg, 5-day release microparticles encapsulated with 5 µg GnRHa/kg BW (PLGA 5), 20 µg GnRHa/kg (PLGA 20), or 1 mL/kg 0.9% NaCl (control). Cumulative percentage ovulation was 100% in the PLGA 5 group, significantly higher than in other tested groups. No differences among groups were observed in latency or fecundity. The level of 11-ketotestosterone (11-KT) peaked at 40 h post-injection, and was sustained during ovulation, in all treated groups. The 17β-estradiol (E2) concentration increased in the mGnRHa-only group immediately after hormone injection, while both PLGA groups showed a reduction in E2 after injection, continuing to decrease until ovulation. A low dose of mGnRHa in PLGA microparticles significantly improves induction of ovulation and results in acceptable reproductive performance, which may positively affect pikeperch production under controlled conditions.

Effects of gonadotropin-releasing hormone agonist administered in microparticles on sperm quality and quantity, and plasma sex steroid levels in northern pike

Artificial reproduction of northern pike Esox lucius is impeded by the likelihood of obtaining only a small volume of sperm of inconsistent quality. A controlled-release hormone delivery system has the potential to enhance sperm production while avoiding multiple injections The objective of this study was to investigate the effects of mammalian gonadotropin-releasing hormone agonist (mGnRHa) incorporated into poly(lactic-co-glycolic acid) (PLGA) microparticles on milt production, spermatozoon characteristics, and secretion of 17β-estradiol (E2), 11-keto testosterone (11-KT), and testosterone in northern pike. Fish were divided into four groups and injected with 2 mg/kg BW carp pituitary extract (CPE), 20 µg/kg BW mGnRHa in PLGA microparticles, or 20 µg/kg BW mGnRHa plus 20 mg/kg BW metoclopramide (MET) in PLGA microparticles (PLGA + MET), along with a control group injected with 1 ml/kg 0.9% NaCl. At 48 h postinjection, the volume of milt produced was significantly greater in groups treated with CPE and PLGA + MET than in other groups. At 96 h postinjection, all hormone-treated groups exhibited significantly higher spermatozoon average velocity than recorded in the control group. Spermatozoon motility was significantly increased (P < 0.05) in the CPE and PLGA groups compared to baseline values. All treated groups showed significantly lower levels of 11-KT after the hormone injection compared to baseline values and to controls. Plasma testosterone levels increased in all hormone-treated groups. The use of PLGA microparticles, with or without metoclopramide, is suitable for use as a carrier of hormone treatments to regulate spermiation in mature northern pike.

A half century of fish gonadotropin-releasing hormones: Breaking paradigms.

The field of fish gonadotropin-releasing hormones (GnRHs) is also celebrating its 50th anniversary this year. This review provides a chronological history of fish GnRH biology over the past five decades. It demonstrates how discoveries in fish regarding GnRH and GnRH receptor multiplicity, dynamic interactions between GnRH neurons, and additional neuroendocrine factors acting alongside GnRH, amongst others, have driven a paradigm shift in our understanding of GnRH systems and functions in vertebrates, including mammals. The role of technological innovations in enabling scientific discoveries is portrayed, as well as how fundamental research in fish GnRH led to translational outcomes in aquaculture. The interchange between fish and mammalian GnRH research is discussed, as is the value and utility of using fish models for advancing GnRH biology. Current challenges and future perspectives are presented, with the hope of expanding the dialogue and collaborations within the neuroendocrinology scientific community at large, capitalizing on diversifying model animals and the use of comparative strategies.

GnRH-Related Neurohormones in the Fruit Fly Drosophila melanogaster.

Genomic and phylogenetic analyses of various invertebrate phyla revealed the existence of genes that are evolutionarily related to the vertebrate’s decapeptide gonadotropin-releasing hormone (GnRH) and the GnRH receptor genes. Upon the characterization of these gene products, encoding peptides and putative receptors, GnRH-related peptides and their G-protein coupled receptors have been identified. These include the adipokinetic hormone (AKH) and corazonin (CRZ) in insects and their cognate receptors that pair to form bioactive signaling systems, which network with additional neurotransmitters/hormones (e.g., octopamine and ecdysone). Multiple studies in the past 30 years have identified many aspects of the biology of these peptides that are similar in size to GnRH and function as neurohormones. This review briefly describes the main activities of these two neurohormones and their receptors in the fruit fly Drosophila melanogaster. The similarities and differences between Drosophila AKH/CRZ and mammalian GnRH signaling systems are discussed. Of note, while GnRH has a key role in reproduction, AKH and CRZ show pleiotropic activities in the adult fly, primarily in metabolism and stress responses. From a protein evolution standpoint, the GnRH/AKH/CRZ family nicely demonstrates the developmental process of neuropeptide signaling systems emerging from a putative common ancestor and leading to divergent activities in distal phyla.

Comparison of artificial spawning effectiveness of hCG, CPH and GnRHa in combination with dopamine inhibitors in a wild strain of ide Leuciscus idus (L.) in hatchery conditions

Optimization of artificial reproduction, by increasing the survival rate of embryos and hatching rate, is of major importance for reducing genetic diversity, especially in fish captured from their natural habitat that subsequently spawn in hatcheries. The artificial reproduction of ide, Leuciscus idus (L.) was conducted in controlled conditions. The spawning agents included: different doses of human chorionic gonadotropin (hCG) that was compared with common carp pituitary homogenate (CPH), Ovopel – a commercial agent for induction of spawning that contains mammalian gonadotropin releasing hormone analogue (mGnRHa) with dopamine antagonists (DA): metoclopramide (MET) and Ovaprim – a commercial agent containing salmon gonadotropin releasing hormone analogue (sGnRHa) and a dopamine antagonists (DA): domperidone (DOM). There were no ovulations in females from control groups. There were no differences between the ovulation rates (90 %) or embryo survival (> 92 %) and hatching rates (> 91 %) when there was administration of hCG doses between 500 and 1000 IU/kg. When there was comparison of different spawning agents, the ovulation rate was 100 % for all treated groups. There were the shortest and longest latency times to the time of ovulation after administration of CPH (26 h) and hCG (79 h), respectively. The greatest embryo survival (> 93 %) and hatching (> 91 %) rates occurred as a result of hCG administration with these values being slightly greater than when there was treatment with Ovaprim. The association between latency time and hatching rate indicated that when there was a slower final oocyte maturation (FOM) there were greater hatching rates.

Neuropeptidergic modulation of GnRH neuronal activity and GnRH secretion controlling reproduction: insights from recent mouse studies

Gonadotropin-releasing hormone (GnRH) secretion from GnRH neurons and its modulation by neuropeptides are essential for mammalian reproduction. Here, I review the neuropeptides that have been shown to act directly and that may also act indirectly, on GnRH neurons, the reproduction-related processes with which the neuropeptides may be associated or the physiological information they may convey, as well as their cognate receptors, signaling pathways and roles in the modulation of GnRH neuronal firing, [Ca2+]i, GnRH secretion and reproduction. The review focuses on recent research in mice, which offer the most tractable experimental system for studying mammalian GnRH neurons.

Immunohistochemical study of gonadotropin-releasing hormone and somatolactin during induced spawning of Liza ramada

Introduction: Gonadotropin releasing hormone (GnRH) is a crucial regulator of gonadal development and reproduction in fish. In addition, it is a possible secretagogue of somatolactin (SL) in teleosts. Little is known about the possible association of GnRH and SL during reproduction of Liza ramada.Aim of the work: The present study was designed to investigate the GnRH and SL immunoreactivities during inducing the final stages of maturation, ovulation and spawning of Liza ramada; to assess the possible actions of these hormones on sexual maturation and spawning of teleosts.Materials and Methods: Histological and immunohistochemical techniques were generally performed to describe the immunoreactivity of both GnRH and SL during ovarian maturation and spawning of Liza ramada.Results: The mammalian GnRH (mGnRH) cell bodies were observed in the medulla oblongata. However, SL-immunoreactive (-IR) cells were detected in the pars intermedia (PI) of the pituitary gland. The GnRH-IR nerve terminals are in close contact with SL-IR pituitary cells. Importantly, the activity of both mGnRH-IR neurons and SL-IR pituitary cells were increased as reflected with the increased cell number and size during sexual maturation and spawning. The activity of these cells was more pronounced as indicated by the increased cells number and size with more immunoreactivity in pre-spawning female. During final maturation and spawning, mGnRH-IR neurons and SL cells showed an increase in the secretory activity as reflected by their small sizes, vacuolated appearance and weak immunoreactivity.Conclusions: Taken together, these findings suggest that the close contact of mGnRH-IR terminals with SL-IR cells in the pituitary, together with the concomitant changes of GnRH and SL immunoreactivity in response to progress in the reproductive events suggest that GnRH may regulate SL release and the regulation of reproductive activity in L. ramada.

Impact of the Cu(II) ions on the chemical and biological properties of goserelin – coordination pattern, DNA degradation, oxidative reactivity and in vitro cytotoxicity

Goserelin acetate (Gos) as a synthetic analog of the mammalian gonadotropin-releasing hormone (GnRH) is widely used in the treatment of sex hormone-related conditions. In this paper we present the chemical and biological aspects of its interaction with Cu(II) ions. The mode of Cu(II) binding and the thermodynamic stability of the obtained complexes were characterized by potentiometry, UV–Vis and CD spectroscopic methods. The DFT calculations were applied in order to investigate and confirm the molecular structure of the studied systems. The experimental and theoretical results clearly indicated the involvement of three nitrogens from the peptide and two oxygens from the acetate moieties in the Cu(II) coordination under physiological conditions. The investigated metallopeptide caused single- and/or double cleavage of the sugar-phosphate backbone of the plasmid DNA in the reaction accompanied by endogenous substances such as hydrogen peroxide or ascorbic acid. The degradation of the DNA molecule occurred via the free radical mechanism. Calculations based on measured spectra allowed determining the kinetic parameters of OH formation. The cytotoxic effects of Gos and its metallo-derivative were tested in vitro towards two cancer cell lines (A549 – human lung adenocarcinoma, CT26 – mouse colon carcinoma).

Systemic corazonin signalling modulates stress responses and metabolism in Drosophila.

Stress triggers cellular and systemic reactions in organisms to restore homeostasis. For instance, metabolic stress, experienced during starvation, elicits a hormonal response that reallocates resources to enable food search and readjustment of physiology. Mammalian gonadotropin-releasing hormone (GnRH) and its insect orthologue, adipokinetic hormone (AKH), are known for their roles in modulating stress-related behaviour. Here we show that corazonin (Crz), a peptide homologous to AKH/GnRH, also alters stress physiology in Drosophila. The Crz receptor (CrzR) is expressed in salivary glands and adipocytes of the liver-like fat body, and CrzR knockdown targeted simultaneously to both these tissues increases the fly's resistance to starvation, desiccation and oxidative stress, reduces feeding, alters expression of transcripts of Drosophila insulin-like peptides (DILPs), and affects gene expression in the fat body. Furthermore, in starved flies, CrzR-knockdown increases circulating and stored carbohydrates. Thus, our findings indicate that elevated systemic Crz signalling during stress coordinates increased food intake and diminished energy stores to regain metabolic homeostasis. Our study suggests that an ancient stress-peptide in Urbilateria evolved to give rise to present-day GnRH, AKH and Crz signalling systems.

Identification and characterization of the adipokinetic hormone/corazonin-related peptide signaling system in Rhodnius prolixus.

The mammalian gonadotropin-releasing hormone is evolutionarily related to the arthropod adipokinetic hormone and the recently discovered adipokinetic hormone/corazonin-related peptide (ACP). The function of the ACP signaling system in arthropods is currently unknown. In the present study, we identify and characterize the ACP signaling system in the kissing bug Rhodnius prolixus. We isolated the complete cDNA sequence encoding R. prolixus ACP (Rhopr-ACP) and examined its expression pattern. Rhopr-ACP is predominantly expressed in the central nervous system. In particular, it is found in both the brain and corpus cardiacum (CC)/corpora allata (CA) complex. To gain an insight into its role in R. prolixus, we also isolated and functionally characterized cDNA sequences of three splice variants (Rhopr-ACPR-A, B and C) encoding R. prolixus ACP G protein-coupled receptor (Rhopr-ACPR). Rhopr-ACPR-A has only five transmembrane domains, whereas Rhopr-ACPR-B and C have all seven domains. Interestingly, Rhopr-ACPR-A, B and C were all activated by Rhopr-ACP, albeit at different sensitivities, when expressed in Chinese hamster ovary cells stably expressing the human G-protein G16 (CHO/G16). To our knowledge, this is the first study to isolate a truncated receptor cDNA in invertebrates that is functional in a heterologous expression system. Moreover, Rhopr-ACPR-B and C but not Rhopr-ACPR-A can be coupled with Gq α subunits. Expression profiling indicates that Rhopr-ACPR is highly expressed in the central nervous system, as well as the CC/CA complex, suggesting that it may control the release of other hormones found in the CC in a manner analogous to gonadotropin-releasing hormone. Temporal expression profiling shows that both Rhopr-ACP and Rhopr-ACPR are upregulated after ecdysis, suggesting that this neuropeptide may be involved in processes associated with post-ecdysis.

Use of the gonadotrophin-releasing hormone antagonist azaline B to control the oestrous cycle in the koala (Phascolarctos cinereus).

The present study examined the effectiveness of the gonadotrophin-releasing hormone (GnRH) antagonist azaline B to suppress plasma LH and 17β-oestradiol concentrations in koalas and its potential application for oestrous synchronisation. In Experiment 1, single subcutaneous injections of azaline B successfully blocked the LH response to exogenous mammalian (m) GnRH in a dose-dependent manner; specifically, 0 mg (n = 4) did not suppress the LH response, 1 mg azaline B (n = 6) suppressed the LH response for 24 h (P < 0.05), 3.3 mg azaline B (n = 8) suppressed the LH response significantly in all animals only for 3 h (P < 0.05), although in half the animals LH remained suppressed for up to 3 days, and 10 mg azaline B (n = 4) suppressed the LH response for 7 days (P < 0.05). In Experiment 2, daily 1 mg, s.c., injections of azaline B over a 10-day period during seasonal anoestrus (June-July; n = 6) suppressed (P < 0.01) the LH response to mGnRH consecutively over the 10-day treatment period and, 4 days after cessation of treatment, the LH response had not recovered. Experiment 3 was designed to test the efficacy of daily 1 mg, s.c., azaline B over 10 days to suppress plasma LH and 17β-oestradiol concentrations and ultimately synchronise timed return to oestrus during the breeding season. Although azaline B treatment did not suppress basal LH or 17β-oestradiol, oestrus was delayed in all treated females by 24.2 days, but with high variability (range 9-39 days). Overall, the present study demonstrates that the GnRH antagonist azaline B is able to inhibit the LH response in koalas to exogenous mGnRH and successfully delay the return to oestrus. However, although azaline B clearly disrupts folliculogenesis, it has not been able to effectively synchronise return to oestrus in the koala.

Adipokinetic hormone signalling system in the Chagas disease vector, Rhodnius prolixus.

Neuropeptides and their G protein-coupled receptors are widespread throughout Metazoa and in several cases, clear orthologues can be identified in both protostomes and deuterostomes. One such neuropeptide is the insect adipokinetic hormone (AKH), which is related to the mammalian gonadotropin-releasing hormone. AKH has been studied extensively and is known to mobilize lipid, carbohydrates and proline for energy-consuming activities such as flight. In order to determine the possible roles for this signalling system in Rhodnius prolixus, we isolated the cDNA sequences encoding R. prolixus AKH (Rhopr-AKH) and its receptor (Rhopr-AKHR). We also examined their spatial expression pattern using quantitative PCR. Our expression analysis indicates that Rhopr-AKH is only expressed in the corpus cardiacum of fifth-instars and adults. Rhopr-AKHR, by contrast, is expressed in several peripheral tissues including the fat body. The expression of the receptor in the fat body suggests that AKH is involved in lipid mobilization, which was confirmed by knockdown of Rhopr-AKHR via RNA interference. Adult males that had been injected with double-stranded RNA (dsRNA) for Rhopr-AKHR exhibited increased lipid content in the fat body and decreased lipid levels in the haemolymph. Moreover, injection of Rhopr-AKH in Rhopr-AKHR dsRNA-treated males failed to elevate haemolymph lipid levels, confirming that this is indeed the receptor for Rhopr-AKH.

Local Duplication of Gonadotropin-Releasing Hormone (GnRH) Receptor before Two Rounds of Whole Genome Duplication and Origin of the Mammalian GnRH Receptor

Gonadotropin-releasing hormone (GnRH) and the GnRH receptor (GnRHR) play an important role in vertebrate reproduction. Although many GnRHR genes have been identified in a large variety of vertebrate species, the evolutionary history of GnRHR in vertebrates is unclear. To trace the evolutionary origin of GnRHR we examined the conserved synteny of chromosomes harboring GnRHR genes and matched the genes to linkage groups of reconstructed vertebrate ancestor chromosomes. Consistent with the phylogenetic tree, three pairs of GnRHR subtypes were identified in three paralogous linkage groups, indicating that an ancestral pair emerged through local duplication before two rounds of whole genome duplication (2R). The 2R then led to the generation of six subtypes of GnRHR. Some subtypes were lost during vertebrate evolution after the divergence of teleosts and tetrapods. One subtype includes mammalian GnRHR and a coelacanth GnRHR that showed the greatest response to GnRH1 among the three types of GnRH. This study provides new insight into the evolutionary relationship of vertebrate GnRHRs.

SET Protein Interacts with Intracellular Domains of the Gonadotropin-releasing Hormone Receptor and Differentially Regulates Receptor Signaling to cAMP and Calcium in Gonadotrope Cells

In mammals, the receptor of the neuropeptide gonadotropin-releasing hormone (GnRHR) is unique among the G protein-coupled receptor (GPCR) family because it lacks the carboxyl-terminal tail involved in GPCR desensitization. Therefore, mechanisms involved in the regulation of GnRHR signaling are currently poorly known. Here, using immunoprecipitation and GST pull-down experiments, we demonstrated that SET interacts with GnRHR and targets the first and third intracellular loops. We delineated, by site-directed mutagenesis, SET binding sites to the basic amino acids (66)KRKK(69) and (246)RK(247), located next to sequences required for receptor signaling. The impact of SET on GnRHR signaling was assessed by decreasing endogenous expression of SET with siRNA in gonadotrope cells. Using cAMP and calcium biosensors in gonadotrope living cells, we showed that SET knockdown specifically decreases GnRHR-mediated mobilization of intracellular cAMP, whereas it increases its intracellular calcium signaling. This suggests that SET influences signal transfer between GnRHR and G proteins to enhance GnRHR signaling to cAMP. Accordingly, complexing endogenous SET by introduction of the first intracellular loop of GnRHR in αT3-1 cells significantly reduced GnRHR activation of the cAMP pathway. Furthermore, decreasing SET expression prevented cAMP-mediated GnRH stimulation of Gnrhr promoter activity, highlighting a role of SET in gonadotropin-releasing hormone regulation of gene expression. In conclusion, we identified SET as the first direct interacting partner of mammalian GnRHR and showed that SET contributes to a switch of GnRHR signaling toward the cAMP pathway.

Structural and functional characterization of neuropeptide Y in a primitive teleost, the Japanese eel (Anguilla japonica)

In the present study, the first full-length cDNA encoding Neuropeptide Y (NPY) was cloned from the brain of Japanese eel (Anguilla japonica). The open reading frame of Japanese eel NPY gene is 294bp in length, encoding a precursor protein of 97 amino acids, which contains a 36-amino-acid mature peptide. Sequence analysis showed that the Japanese eel NPY peptide is similar to that of other species. Real-time PCR revealed that NPY in Japanese eel is mainly expressed in the brain, especially in the hypothalamus and the optic tectum thalamus. The effect of a negative energy balance on NPY gene expression was examined subsequently. The mRNA level of NPY in the hypothalamus and the optic tectum thalamus showed a pronounced increase after 4days of food deprivation. The biological activities of Japanese eel NPY were further investigated in vivo and in vitro. Intraperitoneal injection of the NPY peptide into Japanese eel could potently elevate the expression of the mammalian gonadotropin-releasing hormone (mGnRH) in hypothalamus and the follicle-stimulating hormone beta (FSHβ), the luteinizing hormone beta (LHβ) and growth hormone (GH) in pituitary. In static incubation studies, the stimulatory effects of NPY on mGnRH expression in hypothalamic fragments and on FSHβ, LHβ and GH expression in pituitary cells were also observed. However, in vivo and in vitro studies showed that NPY exhibits an inhibitory action on the expression of thyroid-stimulating hormone beta (TSHβ) in pituitary. The results indicate that NPY is involved in the regulation of multiple physiological processes in Japanese eel.

Difference in receptor-binding contributes to difference in biological activity between the unique guinea pig GnRH and mammalian GnRH

In the current study, we compared the in vitro potency of a unique form of gonadotropin-releasing hormone (GnRH) present in the brain of the guinea pig (gpGnRH) with that of mammalian GnRH (mGnRH) as well as their binding affinities to the GnRH receptor. In gpGnRH, the highly conserved histidine in position 2 (His 2) and leucine in position 7 (Leu 7) are substituted by tyrosine and valine, respectively. In vivo, gpGnRH was shown to be less potent than mGnRH, possibly in part because of higher susceptibility to enzymatic degradation. In the present in vitro experiments, we observed that gpGnRH was less potent than mGnRH in stimulating the release of luteinizing hormone (LH) from primary pituitary cell cultures of the rat, and at lower concentrations from primary pituitary cell culture of the guinea pig, too. These results were confirmed by radioligand-binding studies. It is concluded that the lower biological activity of gpGnRH in both rat and guinea pig may be explained by the difference in binding to the target cells, although additional factors such as proteolytic degradation may also contribute to the observed phenomenon.

Intron retention in a salmon gonadotropin releasing-hormone in three species of Chirostoma genus.

Intron retention in a salmon gonadotropin releasing-hormone in three species of Chirostoma genus.

Stimulatory Effects of Egg-Laying Hormone and Gonadotropin-Releasing Hormone on Reproduction of the Tropical Abalone,Haliotis asininaLinnaeus

ABSTRACT Egg-laying hormone (ELH) is a neuropeptide hormone that stimulates ovulation of gastropods, including Aplysia californica and Lymnaea stagnalis. Other neuropeptides, gonadotropin releasing hormones (GnRHs), also play important roles in controlling reproduction in both vertebrates and invertebrates. In the current study, the effects of abalone ELH (aELH) and several GnRHs on somatic growth, sex differentiation, gonad maturation, and spawning of Haliotis asinina were investigated in 3 experiments. In experiment 1, groups of 4-mo-old juveniles (11.8 ± 0.03 mm shell length (SL) and 0.33 ± 0.04 g body weight (BW)) were injected with aELH and GnRHs, including buserelin (mammalian GnRH analogue), octopus GnRH (octGnRH), and tunicate GnRH-I (tGnRH-I), at doses of 20 ng/g BW and 200 ng/g BW. The aELH induced early sex differentiation with a bias toward females, but with normal somatic growth, whereas the different isoforms of GnRH had no effect on sexual differentiation or somatic growth. In experiment 2,...