Pituitary Gene Expression Research Articles

Effect of long-term food restriction on reproductive performances in female yellowtail, Seriola quinqueradiata

In aquaculture of species with a large body size, such as tuna and yellowtail, a major profitability concern is that broodstock management for egg collection incurs high feeding costs and labor. In order to reduce feeding costs, development of restricted feeding techniques without affecting the reproductive performance may be useful. To gain a better understanding of the potential significance of capital energy in reproduction of large fish with income breeding patterns, we examined the effects of long-term restricted feeding prior to the onset of oocyte development on reproductive performance in female yellowtail (Seriola quinqueradiata). A control group was fed to satiety, while experimental groups were restricted to 50 and 25% of the ration administered to the control group from July to December. The females subjected to restricted feeding had lower ovary weight and smaller ovarian follicles than did the control females in February. Moreover, plasma 17β-estradiol levels in food-restricted females were significantly lower than those in normally fed females in January and February. Furthermore, we found that food-restricted females had lower pituitary gene expression levels of gonadotropins (follicle-stimulating hormone and luteinizing hormone) in January. These results suggest that severe food restriction during the immature phase delays initiation of oocyte development via an alteration in pituitary gonadotropin production in yellowtail females. Once food intake was sufficient after switching to the satiation feeding regime, however, oocyte development rapidly advanced, resulting in the production of fully functional eggs. Overall, these findings demonstrate that the yellowtail displays a mixed strategy of capital-breeding patterns at the onset of sexual maturation, but stronger income-breeding patterns with its progression in reproduction with energy acquired during the vitellogenic phase. Additionally, food deprivation over 6months by 50% of the amount of food required for satiation during the immature phase did not change reproductive performance in female yellowtail, although the females in the 25% feeding group showed a lower percentage of normally hatching eggs. Therefore, a 50% restricted feeding regime before the onset of sexual maturation is acceptable for reducing feeding costs in broodstock management without affecting reproductive performance.

Time- and dose-related effects of a gonadotropin-releasing hormone agonist and dopamine antagonist on reproduction in the Northern leopard frog (Lithobates pipiens)

Gonadotropin-releasing hormone (GnRH) stimulates luteinizing hormone release to control ovulation and spermiation in vertebrates. Dopamine (DA) has a clear inhibitory role in the control of reproduction in numerous teleosts, and emerging evidence suggests that similar mechanisms may exist in amphibians. The interactions between GnRH and DA on spawning success and pituitary gene expression in the Northern leopard frog (Lithobates pipiens) were therefore investigated. Frogs were injected during the natural breeding season with a GnRH agonist [GnRH-A; (Des-Gly10, D-Ala6, Pro-NHEt9)-LHRH; 0.1μg/g and 0.4μg/g] alone and in combination with the dopamine receptor D2 antagonist metoclopramide (MET; 5μg/g and 10μg/g). Injected animals were allowed to breed in outdoor mesocosms. Time to amplexus and oviposition were assessed, and egg mass release, incidences of amplexus, egg mass weight, total egg numbers and fertilization rates were measured. To examine gene expression, female pituitaries were sampled at 12, 24 and 36h following injection of GnRH-A (0.4μg/g) alone and in combination with MET (10μg/g). The mRNA levels of the genes lhb, fshb, gpha, drd2 and gnrhr1 were measured using quantitative real-time PCR. Data were analyzed by a two-way ANOVA. Both GnRH-A doses increased amplexus, oviposition and fertilization alone. Co-injection of MET with GnRH-A did not further enhance spawning success. Injection of GnRH-A alone time-dependently increased expression of lhb, fshb, gpha and gnrhr1. The major effect of MET alone was to decrease expression of drd2. Importantly, the stimulatory effects of GnRH-A on lhb, gpha and gnrhr1 were potentiated by the co-injection of MET at 36h. At this time, expression of fshb was increased only in animals injected with both GnRH-A and MET. Spawning success was primarily driven by the actions of GnRH-A. The hypothesized inhibitory action of DA was supported by pituitary gene expression analysis. The results from this study provide a fundamental framework for future time- and dose–response investigations to improve current spawning methods in amphibians.

Tilapia adropin: the localization and regulation of growth hormone gene expression in pituitary cells

The peptide hormone adropin, encoded by the energy homeostasis-associated (Enho) gene, plays a role in energy homeostasis and the control of vascular function. The aim of this study was to examine the role of adropin in growth hormone (GH) gene expression at the pituitary level in tilapia. As a first step, the antiserum for the tilapia adropin was produced, and its specificity was confirmed by antiserum preabsorption and immunohistochemical staining in the tilapia pituitary. Adropin could be detected immunocytochemically in the proximal pars distalis (PPD) of the tilapia pituitary. In primary cultures of tilapia pituitary cells, tilapia adropin was effective in increasing GH mRNA levels. However, removal of endogenous adropin by immunoneutralization using adropin antiserum inhibited GH gene expression. In parallel experiments, pituitary cells co-treated with ovine pituitary adenylate cyclase activating polypeptide 38 (oPACAP38) and adropin showed a similar increase level compared to those treated with oPACAP38 alone, whereas insulin-like growth factor 1 (IGF1) not only had an inhibitory effect on basal GH mRNA levels, but also could abolish adropin stimulation of GH gene expression. In pituitary cells pretreated with actinomycin D, the half-life of GH mRNA was enhanced by adropin. Taken together, these findings suggest that adropin may serve as a novel local stimulator for GH gene expression in tilapia pituitary.

Irisin stimulates gonadotropins gene expression in tilapia (Oreochromis niloticus) pituitary cells

The link between energy metabolism and reproduction is well known in vertebrates. Irisin, the product of fibronectin type III domain-containing protein 5 (FNDC5) gene, plays an important role in energy homeostasis. However, biological actions of irisin on reproduction remain elusive. To address this gap, we examined the direct effects of irisin on luteinizing hormone β (LHβ) and follicle-stimulating hormone β (FSHβ) gene expression in tilapia pituitary cells. As a first step, the transcripts of FNDC5 were detected in the proximal pars distalis (PPD), but not in the rostral pars distalis (RPD) and neurointermediate lobe (NIL) of the tilapia pituitary by RT-PCR. In the tilapia pituitary, irisin immunoreactive signals were also detected in PPD region. In primary cultures of tilapia pituitary cells, irisin was effective in stimulating both LHβ and FSHβ mRNA levels in vivo and in vitro. In cultured pituitary cells of tilapia, removal of endogenous irisin by immunoneutralization using irisin antiserum inhibited LHβ and FSHβ gene expression. Salmon gonadotrophin releasing hormone (sGnRH) increased LHβ and FSHβ mRNA levels in tilapia pituitary but these stimulatory actions were not either enhanced by treatment with irisin or blocked by irisin antiserum. Furthermore, the stimulation on LHβ and FSHβ mRNA expression was coincident with the enhancement of LHβ and FSHβ mRNA stability after irisin treatment. These results provide evidence that irisin may serve as a novel intrapituitary factor maintaining gonadotropins gene expression in tilapia pituitary.

Effect of timing of restricted feeding on sexual maturation in female yellowtail, Seriola quinqueradiata

In aquaculture of species with a large body size such as tuna and yellowtail, a major problem still is that broodstock management for egg collection requires high feeding cost and labor. In order to reduce feeding costs, development of restricted feeding techniques without affecting the reproductive performance may be useful. To gain a better understanding of reproductive responses to food supply, we examined the effect of restricted feeding during the previtellogenic and vitellogenic phases on sexual maturation in female yellowtail, Seriola quinqueradiata. Restricted feeding during the vitellogenic phase tended to reduce ovary weight relative to normally fed controls at the end of the experiment. Histological observations revealed that both restricted feeding regimes do not affect the percentage of atretic follicles as compared to the control group. Nevertheless, the mean diameter of the most advanced follicles of the females subjected to restricted feeding during the vitellogenic phase was significantly smaller to normally fed controls. These results suggest that reduced food intake during the vitellogenic phase is likely to delay oocyte growth, and lead to low ovarian weight. Endocrine analyses showed that restricted feeding during the vitellogenic phase reduced plasma 17β-estradiol levels, but not plasma and pituitary gene expression levels of gonadotropins (follicle-stimulating hormone and luteinizing hormone) at the end of the experiment. Transcripts for ovarian steroidogenesis-related genes, such as P450 side-chain cleavage (cyp11a1) and 3β-hydroxysteroid dehydrogenase (hsd3b) after food restriction during the vitellogenic phase tended to be high. Therefore, the effects of restricted feeding on reproduction would not be mediated by alterations in circulating gonadotropin levels, but rather through direct effects on the ovarian steroid production in yellowtail females.

Effects of active immunization against GnRH versus surgical castration on hypothalamic-pituitary function in boars

The objective was to compare effects of anti-GnRH immunization (immunocastration) versus surgical castration on hypothalamic-pituitary function in boars. Thirty-six boars were randomly divided into three groups (n = 12/group): control, surgically castrated, or immunized against GnRH at 10 wk of age (boostered 8 wk later). Compared to intact boars, immunocastration reduced (P < 0.05) serum concentrations of LH, FSH, testosterone and inhibin B and caused severe testicular atrophy, whereas surgical castration increased (P < 0.05) serum concentrations of LH and FSH. Both immunocastration and surgical castration consistently reduced hypothalamic GnRH synthesis, with decreased (P < 0.05) mRNA expressions of GnRH, GnRH up-stream gatekeeper genes kiss1 and its receptor (GPR54), and androgen receptor in the hypothalamic arcuate nucleus (ARC) and anteroventral periventricular nucleus (AVPV), as well as GnRH content in the median eminence. Inconsistently, mRNA expressions of gonadotropin-inhibitory hormone (GnIH) in ARC and AVPV as well as its receptor (GPR147) in pituitary were selectively reduced (P < 0.05), but mRNA expressions of estrogen receptor alpha and aromatase (CPY17A1) in pituitary were selectively increased (P < 0.05) in surgical castrates. In response to selectively attenuated suppressive signaling from GnIH and testosterone, mRNA expressions of GnRH receptor (GnRHR), LH-β and FSH-β in pituitary were increased (P < 0.05) in surgical castrates, whereas these pituitary gene expressions were decreased (P < 0.05) in immunocastrates, due to loss of hypothalamic GnRH signaling. We concluded that immunocastration and surgical castration consistently reduced hypothalamic GnRH synthesis due to a testosterone deficiency disrupting testosterone-Kisspeptin-GPR54-GnRH signaling pathways. Furthermore, selectively attenuated GnIH and testosterone signaling in the pituitary increased gonadotropin production in surgical castrates.

Mechanisms for PACAP-induced prolactin gene expression in grass carp pituitary cells.

In mammals, pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic hormone with diverse functions but its role in prolactin (PRL) regulation is highly controversial. To shed light on Prl regulation by PACAP in fish model, grass carp pituitary cells was used as a model to examine the receptor specificity and signal transduction for PACAP modulation of prl gene expression in the carp pituitary. Using RT-PCR, PACAP-selective PAC1 receptor was detected in carp lactotrophs. In carp pituitary cells, nanomolar doses of PACAP, but not VIP, could elevate Prl secretion and protein production with concurrent rise in prl mRNA and these stimulatory effects were blocked by PACAP antagonist but not VIP antagonist. PACAP-induced prl mRNA expression could be mimicked by activating adenylate cyclase (AC), increasing cAMP level by cAMP analog, or increasing intracellular Ca2+ ([Ca2+]i) by Ca2+ ionophore/voltage-sensitive Ca2+ channel (VSCC) activator. PACAP-induced prl gene expression, however, was attenuated/abolished by suppressing cAMP production, inhibiting PKA activity, blocking [Ca2+]i mobilization and VSCC activation, calmodulin (CaM) antagonism, and inactivation of JNK and CaM Kinase II (CaMK-II). Similar sensitivity to CaM, JNK, and CaMK-II blockade was also noted by substituting cAMP analog for PACAP as the stimulant for prl mRNA expression. These results, as a whole, provide evidence for the first time that (i) PACAP activation of PAC1 receptor expressed in carp lactotrophs could induce Prl synthesis and secretion, and (ii) Prl production induced by PACAP was mediated by upregulation of prl gene expression, presumably via functional coupling of cAMP/PKA-, Ca2+/CaM-, and MAPK-dependent cascades.

Novel Functional Role of NK3R Expression in the Potentiating Effects on Somatolactin α Autoregulation in grass carp pituitary cells.

In our previous study, NKB/NK3R system has been shown to act at the pituitary level to up-regulate SLα synthesis and secretion in grass carp. However, whether NK3R expression can serve as a regulatory target at the pituitary level and contribute to NKB interactions with other SLα regulators is still unclear. In current study, using grass carp pituitary cells as a model, we have a novel finding that co-treatment of SLα/SLβ with carp TAC3 gene products, could induce a noticeable enhancement in SLα mRNA expression and these potentiating effects occurred with a parallel rise in NK3R transcript level after SLα/SLβ treatment. Interestingly, the stimulatory effects of SLα/SLβ on NK3R gene expression could be further potentiated by co-treatment with IGF-I/-II and simultaneous exposure of carp pituitary cells to SLα/SLβ and IGF-I/-II in the presence of TAC3 gene products was found to markedly elevated SLα mRNA expression (20 fold increase) and this synergistic stimulation was mediated by cAMP/PKA-, PLC/PKC- and Ca2+ -dependent cascades functionally coupled with NK3R activation. These findings suggest that local release of SLα via functional interactions with IGF-I/-II and TAC3/NK3R system may constitute a potent stimulatory signal for SLα gene expression in the carp pituitary via up-regulation of NK3R expression.

Chronic diclofenac exposure affects gill integrity and pituitary gene expression and displays estrogenic activity in nile tilapia (Oreochromis niloticus)

Oreochromis niloticus has been exposed to diclofenac (DCF), a nonsteroidal anti-inflammatory drug prevalent in the aquatic environment, for 80 days post-hatch (dph). Concentrations ranged from environmentally relevant (0.1 μg L−1 and 1 μg L−1 DCF) up to 100-fold thereof. Population relevant endpoints (hatching, survival, growth) as well as gill histopathology were analyzed. On this level of examination only gills exhibited mild to moderate alterations. On the contrary, biomarkers associated with reproduction were affected due to DCF exposure, indicating the potential to affect sexual differentiation and gametogenesis by acting as an estrogenic endocrine disrupting compound (EDC) in tilapia. Vitellogenin (VTG) gene expression was significantly induced at 1 μg L−1 DCF. In order to find an explanation, gene expression patterns of key enzymes of the biotransformation phases I, II, and III have been analyzed. It seems very likely that the detoxification metabolism is induced in a dose dependent manner at higher concentrations of DCF leading to the expression pattern of VTG mRNA. Our results suggest that DCF at environmentally relevant concentrations adversely affects O. niloticus gill histopathology and pituitary gene expression, and has the potential to act as an estrogenic EDC. The sensitivity of various endpoints, however, differs and therefore these endpoints should be linked.

Can obestatin modulate the GnRH neurons activity?

Obestatin, an anorexigenic peptide acting at the central nervous system and on the periperial level, can co-create neuroendocrine network, which modulate the gonadotrophic axis activity. The aim of this study was to investigate the role of intracerebroventricular obestatin infusion on the activity of the gonadoliberine (GnRH) neurons activity.The experiment was performed on peripubertal Polish Merino sheep (n=24). Animals were divided into 2 groups: control (Ringer-Lock solution infusions; n=12) and experimental (obestatin infusion, 25μl/120μl/h; n=12). Infusions were performed over three consecutive days; blood samples were collected on day 0 and day 3. After the experiment, the animals were slaughtered, and the chosen brain tissue was preserved for IHC and Real Time RT-qPCR analysis.It was also shown that exogenous obestatin changes the selected gene expression of GnRH pulse generator, decreases the secretory activity of GnRH neurons, resulting from the inhibition of GnRH release from median eminence terminal nerves, and also decreases the GnRH receptor gene expression in pituitary. On the basis of the obtained results it can be concluded that obestatin may be involved in the modulation of reproduction processes in animals at the level of the central nervous system. However, the mechanism of its action requires further research, especially identifying the obestatin receptor itself.

Progress in micro RNA focused research in endocrinology

Micro RNAs (miRNAs) are small regulatory molecules of increasing biologists' interest. miRNAs, unlikely mRNA, do not encode proteins. It is a class of small double stranded RNA molecules that via their seed sequence interact with mRNA and inhibit its expression. It has been estimated that 30% of human gene expression is regulated by miRNAs. One miRNA usually targets several mRNAs and one mRNA can be regulated by several miRNAs. miRNA biogenesis is realized by key enzymes, Drosha and Dicer. miRNA/mRNA interaction depends on binding to RNA-induced silencing complex. Today, complete commercially available methodical proposals for miRNA investigation are available. There are techniques allowing the identification of new miRNAs and new miRNA targets, validation of predicted targets, measurement of miRNAs and their precursor levels, and validation of physiological role of miRNAs under in vitro and in vivo conditions. miRNAs have been shown to influence gene expression in several endocrine glands, including pancreas, ovary, testes, hypothalamus, and pituitary.

Anti-Müllerian hormone: a new actor of sexual dimorphism in pituitary gonadotrope activity before puberty.

Anti-Müllerian hormone (AMH) contributes to male sexual differentiation and acts on gonads of both sexes. Identification of AMH receptivity in both pituitary and brain has led to the intriguing idea that AMH participates to the hypothalamic-pituitary control of reproduction, however in vivo experimental evidence is still lacking. We show that AMH stimulates secretion and pituitary gene expression of the gonadotropin FSH in vivo in rats. AMH action is sex-dependent, being restricted to females and occurring before puberty. Accordingly, we report higher levels of pituitary AMH receptor transcripts in immature females. We show that AMH is functionally coupled to the Smad pathway in LβT2 gonadotrope cells and dose-dependently increases Fshb transcript levels. Furthermore, AMH was shown to establish complex interrelations with canonical FSH regulators as it cooperates with activin to induce Fshb expression whereas it reduces BMP2 action. We report that GnRH interferes with AMH by decreasing AMH receptivity in vivo in females. Moreover, AMH specifically regulates FSH and not LH, indicating that AMH is a factor contributing to the differential regulation of gonadotropins. Overall, our study uncovers a new role for AMH in regulating gonadotrope function and suggests that AMH participates in the postnatal elevation of FSH secretion in females.

Transcriptomics Modeling of the Late-Gestation Fetal Pituitary Response to Transient Hypoxia.

BackgroundThe late-gestation fetal sheep responds to hypoxia with physiological, neuroendocrine, and cellular responses that aid in fetal survival. The response of the fetus to hypoxia represents a coordinated effort to maximize oxygen transfer from the mother and minimize wasteful oxygen consumption by the fetus. While there have been many studies aimed at investigating the coordinated physiological and endocrine responses to hypoxia, and while immunohistochemical or in situ hybridization studies have revealed pathways supporting the endocrine function of the pituitary, there is little known about the coordinated cellular response of the pituitary to the hypoxia.ResultsThirty min hypoxia (from 17.0±1.7 to 8.0±0.8 mm Hg, followed by 30 min normoxia) upregulated 595 and downregulated 790 genes in fetal pituitary (123–132 days’ gestation; term = 147 days). Network inference of up- and down- regulated genes revealed a high degree of functional relatedness amongst the gene sets. Gene ontology analysis revealed upregulation of cellular metabolic processes (e.g., RNA synthesis, response to estrogens) and downregulation of protein phosphorylation, protein metabolism, and mitosis. Genes found to be at the center of the network of upregulated genes included genes important for purine binding and signaling. At the center of the downregulated network were genes involved in mRNA processing, DNA repair, sumoylation, and vesicular trafficking. Transcription factor analysis revealed that both up- and down-regulated gene sets are enriched for control by several transcription factors (e.g., SP1, MAZ, LEF1, NRF1, ELK1, NFAT, E12, PAX4) but not for HIF-1, which is known to be an important controller of genomic responses to hypoxia.ConclusionsThe multiple analytical approaches used in this study suggests that the acute response to 30 min of transient hypoxia in the late-gestation fetus results in reduced cellular metabolism and a pattern of gene expression that is consistent with cellular oxygen and ATP starvation. In this early time point, we see a vigorous gene response. But, like the hypothalamus, the transcriptomic response is not consistent with mediation by HIF-1. If HIF-1 is a significant controller of gene expression in the fetal pituitary after hypoxia, it must be at a later time.

Cell Type-Specific Sexual Dimorphism in Rat Pituitary Gene Expression During Maturation.

The most obvious functional differences between mammalian males and females are related to the control of reproductive physiology and include patterns of GnRH and gonadotropin release, the timing of puberty, sexual and social behavior, and the regulation of food intake and body weight. Using the rat as the best-studied mammalian model for maturation, we examined the expression of major anterior pituitary genes in five secretory cell types of developing males and females. Corticotrophs show comparable Pomc profiles in both sexes, with the highest expression occurring during the infantile period. Somatotrophs and lactotrophs also exhibit no difference in Gh1 and Prl profiles during embryonic to juvenile age but show the amplification of Prl expression in females and Gh1 expression in males during peripubertal and postpubertal ages. Gonadotrophs exhibit highly synchronized Lhb, Fshb, Cga, and Gnrhr expression in both sexes, but the peak of expression occurs during the infantile period in females and at the end of the juvenile period in males. Thyrotrophs also show different developmental Tshb profiles, which are synchronized with the expression of gonadotroph genes in males but not in females. These results indicate the lack of influence of sex on Pomc expression and the presence of two patterns of sexual dimorphism in the expression of other pituitary genes: a time shift in the peak expression during postnatal development, most likely reflecting the perinatal sex-specific brain differentiation, and modulation of the amplitude of expression during late development, which is secondary to the establishment of the hypothalamic-pituitary-gonadal and -thyroid axes.

Pituitary gene expression differs in D-galactose-induced cell senescence and steroid-induced prolactinomas.

In general, pituitary tumors are benign with low mitotic activity. Premature senescence has been considered to be a significant mechanism underlying this uniquely benign pituitary tumor. The present study aims to compare the expression of the associated proteins involved in premature senescence pathways among normal, aging and pituitary adenoma cells. We successfully induced the aging pituitary using continuous D‑galactose (D‑gal) injection as well as a prolactin‑secreting pituitary tumor via diethylstilbestrol implants. Compared with normal pituitary cells, the aging pituitary tissues revealed increased expression of IL‑6, C/EBPβ, p53, p21 and p16 and decreased expression of pituitary tumor transforming gene. In contrast, the expression of IL‑6, p21 and p16 was decreased in pituitary tumor cells compared with normal pituitary tissues. Taken together, multiple pathways including IL‑6/C/EBPβ, p53/p21 and p16 were activated in aging pituitary cells in response to D‑gal treatment. However, all these pathways were immune to pituitary tumors treated by chronic estrogen. The findings and the involvement of cytokines in a highly prevalent natural disease model (pituitary adenomas) indicate a potential use of this pathway as a target for effective therapy for tumor silencing and prevention of adenoma progression towards malignancy.

Differential stress response in rats subjected to chronic mild stress is accompanied by changes in CRH-family gene expression at the pituitary level

The purpose of this study was to examine molecular markers of the stress response at the pituitary and peripheral levels in animals that responded differently to chronic mild stress (CMS). Rats were subjected to 2-weeks CMS and symptoms of anhedonia was measured by the consumption of 1% sucrose solution. mRNA levels of CRH-family neuropeptides (Crh—corticotropin-releasing hormone, Ucn1—urocortin 1, Ucn2—urocortin 2, Ucn3—urocortin 3), CRH receptors (Crhr1—corticotropin-releasing hormone receptor 1, Crhr2—corticotropin-releasing hormone receptor 2) and Crhbp (corticotropin-releasing factor binding protein) in the pituitaries of rats were determined with real-time PCR. Plasma levels of ACTH (adrenocorticotropin), CRH and urocortins were measured with ELISA assays. CMS procedure led to the development of anhedonia manifested by the decreased sucrose consumption (stress-reactive, SR, stress-susceptible group). Additionally, the group of animals not exhibiting any signs of anhedonia (stress non-reactive, SNR, stress-resilient group) and the group characterized by the increased sucrose consumption (stress invert-reactive group SIR) were selected. The significant increases in ACTH plasma level accompanied by the decreases in the pituitary gene expression of the Crh, Ucn2 and Ucn3 in both stress non-reactive and stress invert-reactive groups were observed. The only molecular change observed in stress-reactive group was the increase in UCN2 plasma level. The differentiated behavioral stress responses were reflected by gene expression changes in the pituitary. Alterations in the mRNA levels of Crh, Ucn2 and Ucn3 in the pituitary might confirm the paracrine and/or autocrine effects of these peptides in stress response. The opposite behavioral effect between SNR vs. SIR groups and the surprising similarity at gene expression and plasma ACTH levels in these two groups may suggest the discrepancy between molecular and behavioral stress responses; however, there results might indicate to similarity underlying different ways to cope with stress conditions.

Cellular distribution of Egr1 transcription in the male rat pituitary gland.

The transcription factor gene Egr1 is necessary for female fertility; EGR1 protein is an established molecular regulator of adult female gonadotroph function where it mediates GNRH-stimulated transcription of the Lhb gene. Recent studies have also implicated pituitary EGR1 in the mediation of other physiological signals indicating an integrative function. However, the role of EGR1 in males is less well defined and this uncertainty is compounded by the absence of cellular expression data in the male pituitary gland. The aim of this study, therefore, was to define the distribution of Egr1 gene expression in the adult male rat pituitary. To further this aim, we have evaluated cellular populations in a transgenic rat model (Egr1-d2EGFP), in which we demonstrate regulated green fluorescent protein (GFP) expression in EGR1+ pituitary cells. Cellular filling by GFP enabled morphological and molecular differentiation of different populations of gonadotrophs; Egr1 transcription and LHB were highly co-localised in a major population of large cells but only minimally co-localised in small GFP+ cells; the latter cells were shown to be largely (80%) composed of minority populations of GH+ somatotrophs (9% of total GH+) and PRL+ lactotrophs (3% of total PRL+). Egr1 transcription was not found in TSH+, ACTH+ or SOX2+ precursor cells and was only minimally co-localised in S-100β+ folliculostellate cells. Our demonstration that the Egr1 gene is actively and selectively transcribed in a major sub-population of male LHB+ cells indicates a largely conserved role in gonadotroph function and has provided a basis for further defining this role.

Zebrafish pituitary gene expression before and after sexual maturation

Sexual maturation and somatic growth cessation are associated with adolescent development, which is precisely controlled by interconnected neuroendocrine regulatory pathways in the endogenous endocrine system. The pituitary gland is one of the key regulators of the endocrine system. By analyzing the RNA sequencing (RNA-seq) transcriptome before and after sexual maturation, in this study, we characterized the global gene expression patterns in zebrafish pituitaries at 45 and 90 days post-fertilization (dpf). A total of 15 043 annotated genes were expressed in the pituitary tissue, 3072 of which were differentially expressed with a greater than or equal to twofold change between pituitaries at 45 and 90 dpf. In the pituitary transcriptome, the most abundant transcript was gh. The expression levels of gh remained high even after sexual maturation at 90 dpf. Among the eight major pituitary hormone genes, lhb was the only gene that exhibited a significant change in its expression levels between 45 and 90 dpf. Significant changes in the pituitary transcripts included genes involved in the regulation of immune responses, bone metabolism, and hormone secretion processes during the juvenile-sexual maturity transition. Real-time quantitative PCR analysis was carried out to verify the RNA-seq transcriptome results and demonstrated that the expression patterns of the eight major pituitary hormone genes did not exhibit a significant gender difference at 90 dpf. For the first time, we report the quantitative global gene expression patterns at the juvenile and sexual maturity stages. These expression patterns may account for the dynamic neuroendocrine regulation observed in body metabolism.

Effect of dietary energy and protein restriction followed by realimentation on pituitary mRNA expression of growth hormone and related genes in lambs

The objective of the current study was to evaluate the influence of dietary energy and protein restriction followed by realimentation on pituitary growth hormone (GH), growth hormone-releasing hormone receptor (GHRHR), GH secretagogue receptor (GHSR), somatostatin receptor 1 (SSTR1), somatostatin receptor 2 (SSTR2), insulin-like growth factor 1 receptor (IGF-1R), and IGF-2 mRNA expression in lambs. Forty 3-month-old native Mongolian wether lambs were selected, and randomly assigned to control group (CON), moderately energy-restricted group (MR1), moderately protein-restricted group (MR2), or severely energy- and protein-restricted group (SR). The feed restriction stage lasted for 60 days and then all groups were fed the same diet for 90 days (realimentation stage). Pituitaries were collected from four lambs in each group at the end of the two stages. Pituitary gene expression was determined by quantitative real-time reverse transcription PCR. At the end of the restriction stage, the body weight of lambs in all restricted groups was significantly lower than that in the CON group. Pituitary GH, GHRHR, GHSR and IGF-2 expression in lambs in the SR group was greater than that in the CON group (P<0.05), whereas the mRNA expression of SSTR1, SSTR2 and IGF-1R did not change (P≥0.05). At the end of the realimentation stage, the body weight of lambs in the MR1 and MR2 groups was not different from that of lambs in the CON group (P>0.05). However, the body weight of lambs in the SR group was still lower than that in the CON group (P<0.05). The pituitary GH expression of lambs in the SR group was still greater (P<0.05) than that of the CON group, whereas expression of the other genes had returned to control levels. No differences were found in pituitary GH and related gene expression in lambs in the MR1 and MR2 groups compared with those in the CON group throughout the entire experiment (P>0.05). Our results indicated that moderate dietary energy and protein restriction did not influence pituitary GH and related gene expression. Only severe energy and protein restriction caused a significant increase in pituitary GH transcription, which lasted throughout the realimentation stage.

Administration of growth hormone and nandrolone decanoate alters mRNA expression of the GABAB receptor subunits as well as of the GH receptor, IGF-1, and IGF-2 in rat brain

ObjectiveThe illicit use of anabolic androgenic steroids (AAS), especially among young adults, is of major concern. Among AAS users it is common to combine the AAS nandrolone decanoate (ND), with intake of growth hormone (GH) and a connection between gonadal steroids and the GH system has been suggested. Both AAS and GH affect functions in the brain, for example those associated with the hypothalamus and pituitary, and several GH actions are mediated by growth factors such as insulin-like growth factor 1 (IGF-1) and insulin-like growth factor 2 (IGF-2). The GABAergic system is implicated in actions induced by AAS and previous studies have provided evidence for a link between GH and GABAB receptors in the brain. Our aim was to examine the impact of AAS administration and a subsequent administration of GH, on the expression of GABAB receptors and important GH mediators in rat brain. DesignThe aim was to investigate the CNS effects of a high-dose ND, and to study if a low, but physiological relevant, dose of GH could reverse the ND-induced effects. In the present study, male rats were administered a high dose of ND every third day during three weeks, and subsequently the rats were given recombinant human GH (rhGH) during ten days. Quantitative PCR (qPCR) was used to analyze gene expression in hypothalamus, anterior pituitary, caudate putamen, nucleus accumbens, and amygdala. ResultsIn the pituitary gland, the expression of GABAB receptor subunits was affected differently by the steroid treatment; the GABAB1 mRNA expression was decreased whereas a distinct elevation of the GABAB2 expression was found. Administration of ND also caused a decrease of GHR, IGF-1, and IGF-2 mRNA expression in the pituitary while the corresponding expression in the hypothalamus, caudate putamen, nucleus accumbens, and amygdala was unaffected. The rhGH administration did not alter the GABAB2 expression but increased the GABAB1 gene expression in the hypothalamus as compared to the AAS treated group. ConclusionsThese results provide new insights on the impact of ND and GH on the brain and highlight the interaction of these hormones with systems influencing GABAB receptor expression. The physiological significance of the observed effects of these hormones is discussed.