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1.
哺乳类和鱼类的促性腺激素(GTH)细胞都是位于腺垂体,所分泌的激素有促卵泡激素(FSH)和促黄体素(LH),促卵泡激素可以促成卵细胞和精子的生成,而促黄体素可以促进孕酮和睾酮的产生,关于促性腺激素细胞的来源有三种假说,在所有的对促性腺激素细胞调节控制的因素中,最重要的是促性腺激素释放激素(GnRH)。文章从促性腺激素细胞的定位、功能、源泉细胞,以及对其调节控制等方面的研究进展作一综述,以期为在实践中加强对动物生殖规律的人工调控提供参考。  相似文献   

2.
Our goal was to identify the cells expressing Pit-1 protein in chicken anterior pituitary. The anterior pituitaries were collected from laying hens after perfusion with formalin-PBS, and fixed with Bouin's fixative followed by paraffin embedding. Sections of the anterior pituitaries were immunostained for Pit-1 in the first staining sequence followed by staining for 6 types of pituitary hormones in the second sequence. Pit-1 positive nuclei were observed in the glandular cells in both the cephalic and caudal lobes. Pit-1 immunoreaction products were colocalized in the glandular cells immunopositive for growth hormone, thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, adrenocorticotropic hormone or prolactin. These results indicate that Pit-1 protein induction occurs in 6 types of glandular cells, suggesting that Pit-1 may regulate hormone synthesis in each glandular cell in the chicken pituitary.  相似文献   

3.
Anterior pituitary somatotroph differentiation occurs during chick embryonic and rat fetal development. A number of findings support the hypothesis that differentiation of these growth hormone (GH) producing cells in the chick and the rat is regulated by adrenal glucocorticoids and thyroid hormones. Somatotroph differentiation can be induced in cultures of chick embryonic and rat fetal pituitary cells with adrenal glucocorticoids and this effect can be modulated by concomitant treatment with thyroid hormones. Plasma levels of thyroid hormones, corticosterone and adrenocorticotropic hormone increase during development, consistent with the ontogeny of somatotrophs. Treatment of chick embryos or rat fetuses with glucocorticoids in vivo induces premature somatotroph differentiation, indicating that the adrenal gland, and ultimately anterior pituitary corticotrophs, may function to regulate pituitary GH cell differentiation during development. Administration of thyroid hormones in vivo also increases somatotrophs prematurely, and administration of the thyroid hormone synthesis inhibitor methimazole inhibits somatotroph differentiation in vivo, suggesting that endogenous thyroid hormone synthesis contributes to normal somatotroph differentiation. Our working model for the regulation of somatotroph differentiation during normal development includes modulation by elements of the hypothalamo-pituitary-adrenal and hypothalamo-pituitary-thyroid axes. Additional research is reviewed defining the mechanism of action for these peripheral hormones in induction of pituitary GH gene expression during development.  相似文献   

4.
Several different amino acids and peptides control secretion of adenohypophysial hormones and this control may be indirect, via the modulation of hypothalamic hormone secretion. Indeed, classical hypothalamic hormones (e.g., gonadotropin-releasing hormone [GnRH], growth hormone-releasing hormone [GHRH], somatostatin, etc.) may be released into the hypothalamo-hypophysial portal vasculature, travel to the adenohypophysis and there stimulate or inhibit secretion of hormones. Alternatively, some amino acids and peptides exert direct stimulatory or inhibitory effects on the adenohypophysis, thereby impacting hormone secretion. In swine, the most extensively studied modulators of adenohypophysial hormone secretion are the excitatory amino acids (ExAA), namely glutamate and aspartate, and the endogenous opioid peptides (EOP). In general, excitatory amino acids stimulate release of luteinizing hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH), and prolactin (PRL). Secretion of adenohypophysial hormones induced by ExAA is primarily, but perhaps not exclusively, a consequence of action at the central nervous system. By acting primarily at the level of the central nervous system, EOP inhibit LH secretion, stimulate GH release and depending on the animal model studied, exert either stimulatory or inhibitory influences on PRL secretion. However, the EOP also inhibited LH release by direct action on the adenohypophysis. More recently, peptides such as neuropeptide-Y (NPY), orexin-B, ghrelin, galanin, and substance P have been evaluated for possible roles in controlling adenohypophysial hormone secretion in swine. For example, NPY, orexin-B, and ghrelin increased basal GH secretion and modulated the GH response to GHRH, at least in part, by direct action on the adenohypophysis. Secretion of LH was stimulated by orexin-B, galanin, and substance P from porcine pituitary cells in vitro. Because the ExAA and various peptides modulate secretion of adenohypophysial hormones, these compounds may play an important role in regulating swine growth and reproduction.  相似文献   

5.
Proliferation of rat skeletal muscle satellite cells was studied in vitro, and their ability to respond to a variety of protein hormones was examined, including: growth hormone, prolactin, luteinizing hormone, thyrotropin and fibroblast growth factor. All experiments were conducted in serum-free medium to avoid complicating interactions with serum constituents such as other hormones or binding proteins. Dose-response curves were constructed for each protein and encompassed the physiological range plus concentrations two to three orders of magnitude greater than the physiological range. Of the proteins examined, the only one shown to have the ability to directly stimulate satellite cell proliferation was fibroblast growth factor. None of the anterior pituitary protein hormones had the ability to interact directly with satellite cells to stimulate proliferation in vitro. Therefore, satellite cells seem to be selective in their response to protein hormones, and the classes identified thus far are hormones in the insulin-like growth factor family and fibroblast growth factor. These two classes of protein hormones are quite different and would not be expected to act through a common pathway. Consequently, we have proposed a dual regulatory system that may allow for local as well as systemic stimulation of satellite cells.  相似文献   

6.
Steroid hormones have a profound influence on the secretion of the gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These effects can occur as a result of steroid hormones modifying the secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus, or a direct effect of steroid hormones on gonadotropin secreting cells in the anterior pituitary gland. With respect to the latter, we have shown that estradiol increases pituitary sensitivity to GnRH by stimulating an increase in expression of the gene encoding the GnRH receptor. Since an estrogen response element (ERE) has not been identified in the GnRH receptor gene, this effect appears to be mediated by estradiol stimulating production of a yet to be identified factor that in turn enhances expression of the GnRH receptor gene. However, the importance of estradiol for enhancing pituitary sensitivity to GnRH during the periovulatory period is questioned because an increase in mRNA for the GnRH receptor precedes the pre-ovulatory rise in circulating concentrations of estradiol. In fact, it appears that the enhanced pituitary sensitivity during the periovulatory period may occur as a result of a decrease in concentrations of progesterone rather than due to an increase in concentrations of estradiol. Estradiol also is capable of altering secretion of FSH and LH in the absence of GnRH. In a recent study utilizing cultured pituitary cells from anestrous ewes, we demonstrated that estradiol induced a dose-dependent increase in secretion of LH, but resulted in a dose-dependent decrease in the secretion of FSH. We hypothesized that the discordant effects on secretion of LH and FSH might arise from estradiol altering the production of some of the intrapituitary factors involved in synthesis and secretion of FSH. To examine this hypothesis, we measured amounts of mRNA for activin B (a factor known to stimulate synthesis of FSH) and follistatin (an activin-binding protein). We found no change in the mRNA for follistatin after treatment of pituitary cells with estradiol, but noted a decrease in the amount of mRNA for activin B. Thus, the inhibitory effect of estradiol on secretion of FSH appears to be mediated by its ability to suppress the expression of the gene encoding activin.  相似文献   

7.
Pituitary cells, collected from five healthy dogs, were cultured and treated with various doses of ovine corticotropin-releasing hormone (CRH), arginine vasopressin (AVP), oxytocin (OT), or angiotensin II (AII) to determine which of these hypothalamic peptides affected adrenocorticotropin (ACTH) secretion. Of the 4 peptides, only CRH significantly increased ACTH secretion from cultured canine anterior pituitary cells. The lowest dose of CRH tested, 0.01 nM, significantly stimulated ACTH release. Co-addition of AVP, OT, or AII with CRH did not increase ACTH secretion beyond that caused by addition of CRH alone. Similarly, neither co-addition of AVP with OT, AVP with AII, or OT with AII significantly stimulated ACTH secretion. These results support a role for CRH in the physiologic regulation of ACTH secretion from the canine anterior pituitary, but do not support regulatory roles for AVP, OT, or AII.  相似文献   

8.
Ghrelin是一种的由28个氨基酸组成的脑肠肽激素,是生长激素促泌素受体的内源性配体,主要由胃的一种内分泌细胞分泌,也分布于其他许多组织中,如下丘脑、垂体和胰腺等。Ghrelin与其特异性受体结合后,会产生一系列生物学效应,如刺激垂体前叶释放生长激素,增加采食,调节能量平衡,促进胃酸分泌和胃肠蠕动等作用。Ghrelin可能是新发现的下丘脑、垂体、胃之间内分泌调节的联系纽带,在动物生产中将起到重要的作用。  相似文献   

9.
Interleukin-6, mainly produced by monocytes and macrophages is known to influence the secretion of anterior pituitary hormones and is, therefore, considered to play an important role in the interaction between the immune system and the endocrine system. However, IL-6 represents not only a lymphocyte message but is also produced within the anterior pituitary. Folliculostellate (FS) cells have been identified as the source of the intrapituitary IL-6 production in the normal pituitary, whereas in pituitary adenomas IL-6 is produced by the tumor cells themselves. The present review summarizes the knowledge about the regulation of the intrapituitary IL-6 synthesis and release in FS cells. Moreover, the possible roles of the intrinsic IL-6 production for function and growth of normal and adenomatous endocrine pituitary cells are discussed.  相似文献   

10.
The control of growth is a complex mechanism regulated by several metabolic hormones including growth hormone (GH) and thyroid hormones. In avian species, as well as in mammals, GH secretion is regulated by hypothalamic hypophysiotropic hormones. Since thyrotropin-releasing hormone (TRH) and growth hormone-releasing factor (GRF) are potent GH secretagogues in poultry, we were interested in determining the influence of daily intravenous administration of either peptide or both simultaneously on circulating GH and IGF-I concentrations and whether an improvement in growth rate or efficiency would be obtained.

Male broiler chicks were injected once daily for a period of 21 days with either GRF (10 μg/kg), TRH (1 μg/kg) or both GRF and TRH (10 and 1 μg/kg respectively) between four and seven weeks of age. On the last day of the experiment, following intravenous injection of TRH, GRF or a combination of GRF and TRH, plasma GH levels were significantly (P<.05) increased to a similar extent in control chicks and in those which had received daily peptide injections for the previous 21 days. Circulating GH levels between 10 and 90 min post-injection were significantly (P<.05) greater and more than additive than GH levels in chicks injected with both GRF and TRH when compared to those injected with either peptide alone. Mean plasma T3 concentrations during that same time period were significantly elevated (P<.05) above saline-injected control chick levels in birds treated with TRH or GRF and TRH respectively, regardless of whether the chicks had received peptide injections for the previous 21 days. There was no evidence of pituitary refractoriness to chronic administration of either TRH or GRF injection in terms of growth or thyroid hormone secretion.

Despite the large elevation in GH concentration each day, growth rate, feed efficiency and circulating IGF-I concentrations were not enhanced. Thus the quantity or secretory pattern of GH secretion induced by TRH or GRF administration was not sufficient to increase plasma IGF-I concentration or growth.  相似文献   


11.
The presence of a receptor for calcitonin (CT) and the effect of chicken CT (cCT) on adrenocorticotropic hormone (ACTH) secretion stimulated by rat/human corticotropin‐releasing hormone (rhCRH) in the hen anterior pituitary were studied. The specific [125I]cCT binding component was present in the plasma membrane of hen anterior pituitary and this binding component had properties of a receptor which has binding specificity to cCT, reversibility, saturable binding, high affinity and limited capacity. When anterior pituitary cells were incubated in vitro, cCT increased the maximal secretion of chicken ACTH stimulated by rhCRH. These results suggest that CT may act directly on the anterior pituitary via its receptor binding and enhances the ACTH secretion by CRH.  相似文献   

12.
To test the hypothesis that orexin-B acts directly on the anterior pituitary to regulate LH and growth hormone (GH) secretion, anterior pituitary cells from prepuberal gilts were studied in primary culture. On day 4 of culture, 10(5) cells/well were challenged with 0.1, 10 or 1000 nM GnRH; 10, 100 or 1000 nM [Ala15]-hGRF-(1-29)NH2 or 0.1, 1, 10 or 100 nM, orexin-B individually or in combinations with 0.1 and 1000 nM GnRH or 10 and 1000 nM GRF. Secreted LH and GH were measured at 4 h after treatment. Basal LH and GH secretion (control; n = 6 pigs) was 183 +/- 18 and 108 +/- 4.8 ng/well, respectively. Relative to control at 4 h, all doses of GnRH and GRF increased (P < 0.0001) LH and GH secretion, respectively. All doses of orexin-B increased (P < 0.01) LH secretion, except for the 0.1 nM dose. Basal GH secretion was unaffected by orexin-B. Addition of 1, 10 or 100 nM orexin-B in combinations with 0.1 nM GnRH increased (P < 0.001) LH secretion compared to GnRH alone. Only 0.1 nM (P = 0.06) and 100 nM (P < 0.001) orexin-B in combinations with 1000 nM GnRH increased LH secretion compared to GnRH alone. All doses of orexin-B in combination with 1000 nM GRF suppressed (P < 0.0001) GH secretion compare to GRF alone, while only 0.1 nM orexin-B in combination with 10 nM GRF suppressed (P < 0.01) GH secretion compared to GRF. These results indicate that orexin may directly modulate LH and GH secretion at the level of the pituitary gland.  相似文献   

13.
Hypothalamic-releasing factors regulate the secretion of anterior pituitary hormones. The anterior pituitary gland secretes the same six hormones as found in mammals: FSH, LH, prolactin, GH (somatotropic hormone), ACTH, and TSH, plus the melanotropic hormone. The endocrine hormones of the avian posterior pituitary gland concerned with reproduction are mesotocin and AVT. The pineal gland, through the secretion of the hormone melatonin, modulates the periodic autonomic functions of the central nervous system. The ovary produces estrogens, progestogens, and androgenic compounds. The testes produce testosterones and progesterone. The thyroid glands produce two hormones, T4 and T3. The avian adrenal glands produce corticosterone and aldosterone. The bursa of Fabricius is considered an endocrine organ since it is involved in the production of humoral factors. The male reproductive system undergoes hormonal changes associated with puberty, the breeding season, and molt. Some avian species undergo a type of disintegration and seasonal reconstruction of the testis and epididymis. The relationship of the ovarian follicular hormones and the plasma hormones varies depending on the stage of the reproductive cycle and the seasonal photostimulation. Female birds may conceive in the absence of a mate as a result of the fertile period phenomena. The blood chemistry of laying birds is different from that seen in nonlaying hens. Domestication has had a definite influence on the hormone cycles of some avian species. This may lead to certain reproductive problems.  相似文献   

14.
The secretion of luteinizing hormone-releasing hormone (LHRH) and its temporal association with pulses of luteinizing hormone (LH) was examined in ovariectomized prepuberal gilts. Push-pull cannulae (PPC) were implanted within the anterior pituitary gland and LHRH was quantified from 10 min (200 microliters) perfusate samples. Serum LH concentrations were determined from jugular vein blood obtained at the midpoint of perfusate collection. Initial studies without collection of blood samples, indicated that LHRH secretion in the ovariectomized gilt was pulsatile with pulses comprised of one to three samples. However, most pulses were probably of rapid onset and short duration, since they comprised only one sample. Greater LHRH pulse amplitudes were associated with PPC locations within medial regions of the anterior pituitary close to the median eminence. In studies which involved blood collection, LH secretion was not affected by push-pull perfusion of the anterior pituitary gland in most gilts, however, adaptation of pigs to the sampling procedures was essential for prolonged sampling. There was a close temporal relationship between perfusate LHRH pulses and serum LH pulses with LHRH pulses occurring coincident or one sample preceding serum LH pulses. There were occasional LHRH pulses without LH pulses and LH pulses without detectable LHRH pulses. These results provide direct evidence that pulsatile LHRH secretion is associated with pulsatile LH secretion in ovariectomized gilts. In addition, PPC perfusion of the anterior pituitary is a viable procedure for assessing hypothalamic hypophyseal neurohormone relationships.  相似文献   

15.
Stressors generally induce a depression of the hypothalamus-pituitary-testis (HPT) system, mediated by the activated hypothalamus-pituitary-adrenocortical (HPA) system, resulting in a fall in plasma luteinising hormone (LH) and testosterone levels. Hypothalamic gonadotrophin-releasing hormone (GnRH) secretion may be suppressed by endogenous opioid peptides (EOP) and/or corticosteroids. The latter dramatically enhance the negative feedback effects of testosterone on both the hypothalamus and pituitary. Pituitary gonadotrophin secretion may be reduced by adrenocorticotrophic hormone or by EOP of hypothalamic or pituitary origin. Decreases in plasma concentrations of testosterone, independent of gonadotrophins, can be induced by corticosteroids. These hormones might reduce the number of Leydig-cell LH-receptors or occupation of LH-receptors. Testicular steroidogenesis may also be inhibited by pro-opiomelanocortin-derived (opioid) peptides secreted by the Leydig cells. There are some indications of increases in LH and testosterone during acute stress and, in dominant male animals, during the stress of social conflict. The latter finding indicates a difference in stress response between dominant and subordinate males. In subordinate males, decreased feedback sensitivity may allow hypersecretion throughout the HPA system. As a result, corticotrophin releasing hormone may induce the release of EOP from the hypothalamus, which inhibit the HPT axis. This inhibition may be enhanced by a corticosteroid-induced decrease in testosterone feedback.  相似文献   

16.
Congenitally primary hypothyroid growth-retarded (grt) mice exhibit a characteristic growth pause followed by delayed onset of pubertal growth. We characterized the developmental pattern of somatotropes, lactotropes and thyrotropes in the anterior pituitary, as well as plasma levels of their secretory hormones, in grt mice. Compared with normal mice, the weight of grt pituitary gland was similar at 8 weeks of age but significantly heavier after 12 weeks of age. Compared with normal mice, there were significantly fewer somatotropes in the grt pituitary until 8 weeks of age, but the number gradually increased up to 48 weeks. The number of lactotropes in grt mice was consistently lower than that in normal mice from 2 through 48 weeks, whereas the number of thyrotropes in the grt pituitary was consistently higher than in the normal pituitary. Thyrotropes in the grt pituitary exhibited hypertrophy and hyperplasia with less intensive thyroid-stimulating hormone (TSH) immunoreactivity than normal thyrotropes. In normal mice, the sum of the relative proportions of these cells plateaued at 8 weeks, where it remained up to 48 weeks of age. In grt mice, these proportions almost reached normal levels at 12 weeks of age but gradually declined after 24 weeks. Plasma growth hormone concentrations did not differ between grt and normal mice until 24 weeks of age. Compared with normal mice, grt mice exhibited significantly lower plasma prolactin and thyroxine levels but higher TSH levels. These findings indicate that development of somatotropes, lactotropes and thyrotropes in grt mice is impaired, being followed by altered hormone secretion.  相似文献   

17.
The aims of the present study were to clarify the effect of kisspeptin10 (Kp10) on the secretion of growth hormone (GH) from bovine anterior pituitary (AP) cells, and evaluate the ability of sex steroid hormones to enhance the sensitivity of somatotrophic cells to Kp10. AP cells prepared from 8–11‐month‐old castrated calves were incubated for 12 h with estradiol (E2, 10?8 mol/L),progesterone (P4, 10?8 mol/L), testosterone (T, 10?8 mol/L), or vehicle only (control), and then for 2 h with Kp10. The amount of GH released in the medium was measured by a time‐resolved fluoroimmunoassay. Kp10 (10?6 or 10?5 mol/L) significantly stimulated the secretion of GH from the AP cells regardless of steroid treatments (P < 0.05), and E2, P4, and T had no effect on this response. The GH‐releasing response to growth hormone‐releasing hormone (GHRH, 10?8 mol/L) was significantly greater than that to Kp10 (P < 0.05). The present results suggest that Kp10 directly stimulates the release of GH from somatotrophic cells and sex steroid hormones do not enhance the sensitivity of these cells to Kp10. Furthermore, they suggest that the GH‐releasing effect of Kp10 is less potent than that of GHRH.  相似文献   

18.
The greater understanding of the somatotropic axis in the lactating dairy cow that has been achieved in recent years is briefly reviewed in this article. Specifically discussed are: the significance of multiple forms of insulin‐like growth factor messenger RNA (ribonucleic acid) caused by alternative splicing, and the possible functions of the various translated extension proteins; the possible roles of multiple sites of growth hormone secretion other than in the pituitary, and the implications for possible autocrine or paracrine growth hormone secretion; the consequences for increased circulating growth hormone half‐life, and possibly biological effectiveness, caused by growth hormone binding proteins; and the increasing evidence for the presence of growth hormone receptors in the bovine mammary gland. The need for further research is highlighted in the present review; published information regarding the bovine, in many of these areas, is still largely insufficient.  相似文献   

19.
Myostatin (MSTN), known as growth and differentiation factor 8 (GDF-8), is a member of the transforming growth factor β (TGF-β) superfamily that negatively regulates skeletal muscle mass. Myostatin binds with high affinity to the receptor serine threonine kinase activin receptor type IIB (ActRIIB). Activins that also belong to the TGF-β superfamily, stimulate follicle-stimulating hormone production in gonadotrophs and suppress growth hormone and adrenocorticotropic hormone production in somatotrophs and corticotrophs, respectively. The aim of the present paper was therefore to clarify the endocrine action of MSTN in adenohypophysis. The present study details the expression and cellular localization of MSTN and ActRIIB in porcine anterior pituitary gland. The mRNA of MSTN and ActRIIB was consistently expressed in RT-PCR. Immunohistochemistry of MSTN and specific hormones showed that MSTN localized in thyrotrophs and gonadotrophs, in which most of the MSTN immunoreactive cells were identified as thyrotrophs. The immunostaining of ActRIIB was restricted to corticotrophs. These results indicate that MSTN was mainly produced in thyrotrophs and its receptor, ActRIIB, was restrictively contained in corticotrophs. Interestingly, thyrotrophs immunoreactive for MSTN were frequently close to corticotrophs immunoreactive for ActRIIB. The present study suggests that MSTN from thyrotrophs may regulate corticotroph function as a paracrine mediator among the porcine anterior pituitary cells.  相似文献   

20.
Physiology of ghrelin and related peptides   总被引：4，自引：0，他引：4  
Growth hormone (GH) released from pituitary under direct control of hypothalamic releasing (i.e., GHRH) and inhibiting (i.e., sst or SRIF) hormones is an anabolic hormone that regulates metabolism of proteins, fats, sugars and minerals in mammals. Cyril Bowers' discovery of GH-releasing peptide (GHRP-6) was followed by a search for synthetic peptide and nonpeptide GH-secretagogues (GHSs) that stimulate GH release, as well as a receptor(s) unique from GHRH receptor. GHRH and GHSs operate through distinct G protein-coupled receptors to release GH. Signal transduction pathways activated by GHS increase intracellular Ca2+ concentration in somatotrophs, whereas GHRH increases cAMP. Isolation and characterization of ghrelin, the natural ligand for GHS receptor, has opened a new era of understanding to physiology of anabolism, feeding behavior, and nutritional homeostasis for GH secretion and gastrointestinal motility through gut-brain interactions. Other peptide hormones (i.e., motilin, TRH, PACAP, GnRH, leptin, FMRF amide, galanin, NPY, NPW) from gut, brain and other tissues also play a role in modulating GH secretion in livestock and lower vertebrate species. Physiological processes, such as neurotransmission, and secretion of hormones or enzymes, require fusion of secretory vesicles at the cell plasma membrane and expulsion of vesicular contents. This process for GH release from porcine somatotrophs was revealed by atomic force microscopy (AFM), transmission electron microscopy (TEM) and immunohistochemical distribution of the cells in pituitary during stages of development.  相似文献   

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