scholarly journals Regulation of PIT-1 Expression By Ghrelin and GHRP-6 Through the GH Secretagogue Receptor

2001 ◽  
Vol 15 (9) ◽  
pp. 1484-1495 ◽  
Author(s):  
Angel García ◽  
Clara V. Alvarez ◽  
Roy G. Smith ◽  
Carlos Diéguez
Keyword(s):  
Pituitary Gland ◽  
Transcriptional Activation ◽  
Anterior Pituitary ◽  
Primary Cultures ◽  
Physiological Role ◽  
Luciferase Expression ◽  
Established Cell Line ◽  
Pituitary Cells ◽  
Endogenous Ligand ◽  
Infant Rat

Abstract GH secretagogues are an expanding class of synthetic peptide and nonpeptide molecules that stimulate the pituitary gland to secrete GH through their own specific receptor, the GH-secretagogue receptor. The cloning of the receptor for these nonclassical GH releasing molecules, together with the more recent characterization of an endogenous ligand, named ghrelin, have unambiguously demonstrated the existence of a physiological system that regulates GH secretion. Somatotroph cell-specific expression of the GH gene is dependent on a pituitary-specific transcription factor (Pit-1). This factor is transcribed in a highly restricted manner in the anterior pituitary gland. The present experiments sought to determine whether the synthetic hexapeptide GHRP-6, a reference GH secretagogue compound, as well as an endogenous ligand, ghrelin, regulate pit-1 expression. By a combination of Northern and Western blot analysis we found that GHRP-6 elicits a time- and dose-dependent activation of pit-1 expression in monolayer cultures of infant rat anterior pituitary cells. This effect was blocked by pretreatment with actinomycin D, but not by cycloheximide, suggesting that this action was due to direct transcriptional activation of pit-1. Using an established cell line (HEK293-GHS-R) that overexpresses the GH secretagogue receptor, we showed a marked stimulatory effect of GHRP-6 on the pit-1 −2,500 bp 5′-region driving luciferase expression. We truncated the responsive region to −231 bp, a sequence that contains two CREs, and found that both CREs are needed for GHRP-6-induced transcriptional activation in both HEK293-GHS-R cells and infant rat anterior pituitary primary cultures. The effect was dependent on PKC, MAPK kinase, and PKA activation. Increasing Pit-1 by coexpression of pCMV-pit-1 potentiated the GHRP-6 effect on the pit-1 promoter. Similarly, we showed that the endogenous GH secretagogue receptor ligand ghrelin exerts a similar effect on the pit-1 promoter. These data provide the first evidence that ghrelin, in addition to its previously reported GH-releasing activities, is also capable of regulating pit-1 transcription through the GH secretagogue receptor in the pituitary, thus giving new insights into the physiological role of the GH secretagogue receptor on somatotroph cell differentiation and function.

scholarly journals Effects of Vasopressin V1b Receptor Deficiency on Adrenocorticotropin Release from Anterior Pituitary Cells in Response to Oxytocin Stimulation

Endocrinology ◽  
2008 ◽  
Vol 149 (10) ◽  
pp. 4883-4891 ◽  
Author(s):  
Kazuaki Nakamura ◽  
Yoko Fujiwara ◽  
Reiko Mizutani ◽  
Atsushi Sanbe ◽  
Noriko Miyauchi ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Receptor Antagonist ◽  
Anterior Pituitary ◽  
Primary Cultures ◽  
Control Level ◽  
Pituitary Cells ◽  
Anterior Pituitary Cells ◽  
V1b Receptor ◽  
Rat Pituitary ◽  
Acth Release

Oxytocin (OT) is one of the secretagogues for stress-induced ACTH release. OT-induced ACTH release is reported to be mediated by the vasopressin V1b receptor in the rat pituitary gland, which contains both OT and V1b receptors. We examined OT-induced ACTH release using primary cultures of anterior pituitary cells from wild-type (V1bR+/+) and V1b receptor knockout (V1bR−/−) mice. OT stimulated similar levels of ACTH release from pituitary cells of V1bR+/+ and V1bR−/− mice. OT-induced ACTH release was significantly inhibited by the selective V1b receptor antagonist SSR149415 and the OT receptor antagonist CL-14-26 in V1bR+/+ mice. In addition, cotreatment with SSR149415 at 10−6m and CL-14-26 at 10−6m inhibited OT-induced ACTH release to the control level inV1bR+/+ mice. In V1bR−/− mice, OT-induced ACTH release was significantly inhibited by CL-14-26 at 10−8m and completely inhibited at 10−7m. These results indicate that OT induces the ACTH response via OT and V1b receptors inV1bR+/+ mice but via only OT receptors in V1bR−/− mice. The gene expression level of the OT receptor was significantly higher in the anterior pituitary gland of V1bR−/− mice than in that of V1bR+/+ mice, suggesting that the OT receptor is up-regulated to compensate for ACTH release under conditions of V1b receptor deficiency.

Effect of hypothalamic neuropeptides on corticotrophin release from quarters of rat anterior pituitary gland in vitro

1984 ◽  
Vol 100 (2) ◽  
pp. 219-226 ◽  
Author(s):  
S. A. Nicholson ◽  
T. E. Adrian ◽  
B. Gillham ◽  
M. T. Jones ◽  
S. R. Bloom
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Low Dose ◽  
Physiological Role ◽  
Anterior Pituitary Gland ◽  
High Concentration ◽  
Response Curves ◽  
Corticotrophin Releasing Factor ◽  
Basal Release

ABSTRACT The effect of six hypothalamic peptides on the basal release of ACTH and that induced by arginine vasopressin (AVP) or by ovine corticotrophin releasing factor (oCRF) from fragments of the rat anterior pituitary gland incubated in vitro was investigated. Dose–response curves to AVP and to oCRF were obtained, and the response to a low dose of oCRF was potentiated by a low dose of AVP. Basal release of ACTH was not affected by any of the peptides in concentrations in the range 10−12 to 10−6 mol/l, and only substance P (SP) and somatostatin (SRIF) inhibited significantly the response to oCRF in a dose-related manner. The responses to a range of doses of oCRF or AVP were reduced by 10−8 and 10 − 6 mol SP or SRIF/1, and to a greater extent by the higher dose. Except in the case of 10−6 mol SRIF/1 on the response to AVP, the response was not further diminished by preincubation of the tissue with the peptide before the stimulating agent was added. The inhibition of the responses to AVP or oCRF by 10−9 mol SP/1 was not potentiated by its combination with either 5 × 10−10 or 10−8 mol SRIF/1; the inhibitory effects were merely additive. The results suggest that although SRIF and SP are able to modulate the release of ACTH from the anterior pituitary gland, they do so only at a high concentration. In the case of SRIF these concentrations are several orders of magnitude higher than those reported to be present in the hypophysial portal blood and therefore a physiological role for this peptide in the control of ACTH secretion is unlikely. J. Endocr. (1984) 100, 219–226

scholarly journals IGF-I regulates pro-opiomelanocortin and GH gene expression in the mouse pituitary gland

2003 ◽  
Vol 178 (1) ◽  
pp. 71-82 ◽  
Author(s):  
J Honda ◽  
Y Manabe ◽  
R Matsumura ◽  
S Takeuchi ◽  
S Takahashi
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Northern Blotting ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Gh Treatment ◽  
Gh Receptor ◽  
Pomc Mrna ◽  
Igf I ◽  
Mouse Pituitary

IGF-I is expressed in somatotrophs, and IGF-I receptors are expressed in most somatotrophs and some corticotrophs in the mouse pituitary gland. Our recent study demonstrated that IGF-I stimulates the proliferation of corticotrophs in the mouse pituitary. These results suggested that somatotrophs regulate corticotrophic functions as well as somatotrophic functions by the mediation of IGF-I molecules. The present study aimed to clarify factors regulating pituitary IGF-I expression and also the roles exerted by IGF-I within the mouse anterior pituitary gland. Mouse anterior pituitary cells were isolated and cultured under serum-free conditions. GH (0.5 or 1 microg/ml), ACTH (10(-8) or 10(-7) M), GH-releasing hormone (GHRH; 10(-8) or 10(-7) M), dexamethasone (DEX; 10(-8) or 10(-7) M) and estradiol-17beta (e2; 10(-11) or 10(-9) M) were given for 24 h. IGF-I mRNA levels were measured using competitive RT-PCR, and GH and pro-opiomelanocortin (POMC) mRNA levels were measured using Northern blotting analysis. GH treatment significantly increased IGF-I mRNA levels (1.5- or 2.1-fold). ACTH treatment did not alter GH and IGF-I mRNA levels. IGF-I treatment decreased GH mRNA levels (0.7- or 0.5-fold), but increased POMC mRNA levels (1.8-fold). GH treatment (4 or 8 microg/ml) for 4 days increased POMC mRNA levels. GHRH treatment increased GH mRNA levels (1.3-fold), but not IGF-I mRNA levels. DEX treatment significantly decreased IGF-I mRNA levels (0.8-fold). e2 treatment did not affect IGF-I mRNA levels. GH receptor mRNA, probably with GH-binding protein mRNA, was detected in somatotrophs, and some mammotrophs and gonadotrophs by in situ hybridization using GH receptor cDNA as a probe. These results suggested that IGF-I expression in somatotrophs is regulated by pituitary GH, and that IGF-I suppresses GH expression and stimulates POMC expression at the transcription level. Pituitary IGF-I produced in somatotrophs is probably involved in the regulation of somatotroph and corticotroph functions.

scholarly journals In Vivo and In Vitro Arsenic Exposition Induces Oxidative Stress in Anterior Pituitary Gland

2016 ◽  
Vol 35 (4) ◽  
pp. 463-475 ◽  
Author(s):  
Sonia A. Ronchetti ◽  
María S. Bianchi ◽  
Beatriz H. Duvilanski ◽  
Jimena P. Cabilla
Keyword(s):  
Oxidative Stress ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Inorganic Arsenic ◽  
Anterior Pituitary Gland ◽  
Pituitary Cells ◽  
Prolactin Release ◽  
Stress Responsive Genes

Inorganic arsenic (iAs) is at the top of toxic metalloids. Inorganic arsenic-contaminated water consumption is one of the greatest environmental health threats worldwide. Human iAs exposure has been associated with cancers of several organs, neurological disorders, and reproductive problems. Nevertheless, there are no reports describing how iAs affects the anterior pituitary gland. The aim of this study was to investigate the mechanisms involved in iAs-mediated anterior pituitary toxicity both in vivo and in vitro. We showed that iAs administration (from 5 to 100 ppm) to male rats through drinking water increased messenger RNA expression of several oxidative stress-responsive genes in the anterior pituitary gland. Serum prolactin levels diminished, whereas luteinizing hormone (LH) levels were only affected at the higher dose tested. In anterior pituitary cells in culture, 25 µmol/L iAs significantly decreased prolactin release in a time-dependent fashion, whereas LH levels remained unaltered. Cell viability was significantly reduced mainly by apoptosis evidenced by morphological and phosphatidylserine externalization studies. This process is characterized by early depolarization of mitochondrial membrane potential and increased levels of reactive oxygen species. Expression of some key oxidative stress-responsive genes, such as heme oxygenase-1 and metallothionein-1, was also stimulated by iAs exposure. The antioxidant N-acetyl cysteine prevented iAs-induced effects on the expression of oxidative stress markers, prolactin release, and apoptosis. In summary, the present work demonstrates for the first time that iAs reduces prolactin release both in vivo and in vitro and induces apoptosis in anterior pituitary cells, possibly resulting from imbalanced cellular redox status.

scholarly journals Reporter Expression, Induced by a Growth Hormone Promoter-Driven Cre Recombinase (rGHp-Cre) Transgene, Questions the Developmental Relationship between Somatotropes and Lactotropes in the Adult Mouse Pituitary Gland

Endocrinology ◽  
2007 ◽  
Vol 148 (5) ◽  
pp. 1946-1953 ◽  
Author(s):  
Raul M. Luque ◽  
Geraldine Amargo ◽  
Shinya Ishii ◽  
Corrinne Lobe ◽  
Roberta Franks ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Transgenic Mouse ◽  
Anterior Pituitary ◽  
Adult Mouse ◽  
Small Subset ◽  
Parental Line ◽  
Pituitary Cells ◽  
Placental Alkaline Phosphatase ◽  
Developmental Studies ◽  
Mouse Pituitary

This report describes the development and validation of the rGHp-Cre transgenic mouse that allows for selective Cre-mediated recombination of loxP-modified alleles in the GH-producing cells of the anterior pituitary. Initial screening of the rGHp-Cre parental line showed Cre mRNA was specifically expressed in the anterior pituitary gland of adult Cre+/− mice and cephalic extracts of e17 Cre+/− fetuses. Heterozygote rGHp-Cre transgenic mice were crossbred with Z/AP reporter mice to generate Cre+/−,Z/AP+/− offspring. In this model system, the GH promoter-driven, Cre-mediated recombination of the Z/AP reporter leads to human placental alkaline phosphatase (hPLAP) expression that serves to mark cells that currently produce GH, in addition to cells that would have differentiated from GH cells but currently do not express the GH gene. Double immunocytochemistry of adult male and female Cre+/−,Z/AP+/− pituitary cells revealed the majority (∼99%) of GH-producing cells of the anterior pituitary also expressed hPLAP, whereas ACTH-, TSH-, and LH-producing cells were negative for hPLAP, confirming previous reports that corticotropes, thyrotropes, and gonadotropes develop independently of the somatotrope lineage. A small subset (∼10%) of the prolactin-producing cells was positive for hPLAP, consistent with previous reports showing lactotropes can arise from somatotropes during pituitary development. However, the fact that 90% of prolactin-producing cells were negative for hPLAP suggests that the majority of lactotropes in the adult mouse pituitary gland develop independently of the somatotrope lineage. In addition to developmental studies, the rGHp-Cre transgenic mouse will provide a versatile tool to study the role of a variety of genes in somatotrope function and neoplastic transformation.

scholarly journals Neuroendocrine Plasticity in the Anterior Pituitary: Gonadotropin-Releasing Hormone-Mediated Movement in Vitro and in Vivo

Endocrinology ◽  
2007 ◽  
Vol 148 (4) ◽  
pp. 1736-1744 ◽  
Author(s):  
Amy M. Navratil ◽  
J. Gabriel Knoll ◽  
Jennifer D. Whitesell ◽  
Stuart A. Tobet ◽  
Colin M. Clay
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Fluorescent Protein ◽  
Cell Movement ◽  
Pituitary Cells ◽  
Rous Sarcoma ◽  
Cytoskeleton Disruption ◽  
Green Fluorescent

The secretion of LH is cued by the hypothalamic neuropeptide, GnRH. After delivery to the anterior pituitary gland via the hypothalamic-pituitary portal vasculature, GnRH binds to specific high-affinity receptors on the surface of gonadotrope cells and stimulates synthesis and secretion of the gonadotropins, FSH, and LH. In the current study, GnRH caused acute and dramatic changes in cellular morphology in the gonadotrope-derived αT3-1 cell line, which appeared to be mediated by engagement of the actin cytoskeleton; disruption of actin with jasplakinolide abrogated cell movement and GnRH-induced activation of ERK. In live murine pituitary slices infected with an adenovirus-containing Rous sarcoma virus-green fluorescent protein, selected cells responded to GnRH by altering their cellular movements characterized by both formation and extension of cell processes and, surprisingly, spatial repositioning. Consistent with the latter observation, GnRH stimulation increased the migration of dissociated pituitary cells in transwell chambers. Our data using live pituitary slices are a striking example of neuropeptide-evoked movements of cells outside the central nervous system and in a mature peripheral endocrine organ. These findings call for a fundamental change in the current dogma of simple passive diffusion of LH from gonadotropes to capillaries in the pituitary gland.

Bradykinin stimulates phosphoinositide metabolism and prolactin secretion in rat anterior pituitary cells

1989 ◽  
Vol 2 (1) ◽  
pp. 47-53 ◽  
Author(s):  
T.H. Jones ◽  
B. L. Brown ◽  
P. R. M. Dobson
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Inositol Phosphate ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Pituitary Cells ◽  
Phosphoinositide Metabolism ◽  
Phosphate Accumulation ◽  
Anterior Pituitary Cells ◽  
Inositol Phosphate Accumulation

ABSTRACT Bradykinin stimulated prolactin secretion from monolayer cultures of rat anterior pituitary cells, the stimulation being greater from the cells of male rats. This stimulated secretion was accompanied by a rise in total inositol phosphate accumulation, suggesting that the action of bradykinin is mediated by phosphoinositide hydrolysis. The increase in inositol phosphate accumulation was biphasic; a further sharp rise occurred when the concentration of bradykinin exceeded 1 μmol/l. This may indicate that bradykinin acts on other cell types in the pituitary gland. Bradykinin had no effect on growth hormone secretion from cells of normal pituitary glands, or on prolactin secretion and phosphoinositide metabolism in GH3 rat pituitary tumour cells. Bradykinin receptor antagonists (both B1 and B2) had no effect on either bradykinin-stimulated inositol phosphate accumulation or prolactin secretion. Kallikreins, the enzymes responsible for the generation of kinins, are known to be present in the adenohypophysis. Therefore, the results presented here would suggest that kinins may have a role as paracrine agents in the pituitary gland.

scholarly journals Cell Type-Specific Metabolism of Peptidylglycineα -Amidating Monooxygenase in Anterior Pituitary*

Endocrinology ◽  
2000 ◽  
Vol 141 (8) ◽  
pp. 3020-3034 ◽  
Author(s):  
Rajaa El Meskini ◽  
Richard E. Mains ◽  
Betty A. Eipper
Keyword(s):  
Anterior Pituitary ◽  
Secretory Granules ◽  
Primary Cultures ◽  
Cell Types ◽  
Pituitary Cell ◽  
Male Rat ◽  
Pituitary Cells ◽  
Cell Type ◽  
Cell Content ◽  
Monooxygenase Activity

Peptidylglycine α-amidating monooxygenase (PAM) is a bifunctional enzyme expressed in each major anterior pituitary cell type. We used primary cultures of adult male rat anterior pituitary to examine PAM expression, processing, and secretion in the different pituitary cell types and to compare these patterns to those observed in transfected AtT-20 corticotrope tumor cells. Immunostaining and subcellular fractionation identified PAM in pituitary secretory granules and additional vesicular compartments; in contrast, in AtT-20 cells, transfected PAM was primarily localized to the trans-Golgi network. PAM expression was highest in gonadotropes, with moderate levels in somatotropes and thyrotropes and lower levels in corticotropes and lactotropes. Under basal conditions, less than 1% of the cell content of monooxygenase activity was secreted per h, a rate comparable to the basal rate of release of individual pituitary hormones. General secretagogues stimulated PAM secretion 3- to 5-fold. Stimulation with specific hypothalamic releasing hormones demonstrated that different pituitary cell types secrete characteristic sets of PAM proteins. Gonadotropes and thyrotropes release primarily monofunctional monooxygenase. Somatotropes secrete primarily bifunctional PAM, whereas corticotropes secrete a mixture of mono- and bifunctional proteins. As observed in transfected AtT-20 cells, pituitary cells rapidly internalize the PAM/PAM-antibody complex from the cell surface. The distinctly different steady-state localizations of endogenous PAM in primary pituitary cells and transfected PAM in AtT-20 cell lines may simply reflect the increased storage capacity of primary pituitary cells.

scholarly journals LOCALIZATION OF PHOSPHATASE ACTIVITIES IN THE RAT ANTERIOR PITUITARY GLAND

1972 ◽  
Vol 20 (1) ◽  
pp. 1-12 ◽  
Author(s):  
GEORGES PELLETIER ◽  
ALEX B. NOVIKOFF
Keyword(s):  
Golgi Apparatus ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Secretory Cell ◽  
Cell Types ◽  
Anterior Pituitary Gland ◽  
Pituitary Cells ◽  
Blood Capillaries ◽  
Phosphatase Activities ◽  
Thiamine Pyrophosphatase

All five known secretory cell types of the rat anterior pituitary gland display nucleoside diphosphatase (NDPase) activity throughout the endoplasmic reticulum (ER), including the nuclear envelope but not the specialized region of ER at the inner aspect of the Golgi apparatus known as GERL. The functions of the ER diphosphatase are currently unknown. However, speculations concerning its association with glucuronyl transferase may focus on the metabolic roles of the ER in pituitary cells other than those directly related to secretory protein transport. The gonadotrophs have been studied for thiamine pyrophosphatase and acid phosphatase activities as well as NDPase activity. The results suggest that the secretory granules of gonadotrophs arise from GERL and not from the inner element of the Golgi apparatus. The innermost Golgi element of this cell type shows NDPase and thiamine pyrophosphatase activities and appears to be composed, in part at least, of anastomosing tubules. Nucleoside phosphatase activity is also present at the surfaces of all five secretory cell types and between the cells and adjacent blood capillaries.

Sign in / Sign up

Export Citation Format

Share Document