In vivo and in vitro effects of dexamethasone on pituitary thyrotrophin-releasing hormone-like peptide concentrations in the rat

Abstract The novel peptide, pyroglutamyl-glutamyl-proline amide (pGlu-Glu-ProNH2; EEP), which has structural and immunological similarities to TRH (pGlu-His-ProNH2) has recently been shown to contribute to total TRH-like immunoreactivity (t-TRH-LI) detected in the rabbit prostate and rat and porcine anterior pituitary. In this study, the effects of dexamethasone (DEX) on rat pituitary TRH-like peptide levels in the rat were determined. TRH-like immunoreactivity (TRH-LI) was separated by ion exchange chromatography and detected by TRH RIA. Anion exchange chromatographic analysis suggested that EEP-like immunoreactivity (EEP-LI) accounted for 15·0 ± 1·2 pmol t-TRH-LI/g (70·4 ± 3·9%) in the control anterior pituitary with the remaining t-TRH-LI being due to TRH-LI. Following DEX treatment pituitary EEP-LI and TRH-LI increased by 200% and 400% (P<0·001) respectively, constituting a 2·5-fold increase in t-TRH-LI in the pituitary. TRH-LI now accounted for 45·7±5·3% of t-TRH-LI compared with 29·6 ±4·1% in the controls. TRH-LI, but not EEP-LI, was detected in the hypothalamus and posterior pituitary, suggesting that EEP-LI is synthesised within the anterior pituitary. DEX also caused a 2·6-fold rise (P<0·001) in t-TRH-LI in dispersed, cultured anterior pituitary cells. Chromatographic analysis of cultured pituitary cell extracts revealed that the majority of t-TRH-LI (>98%) was due to TRH-LI. A possible explanation for the change in EEP-LI and TRH-LI levels in the in vivo and in vitro pituitary samples is that hypothalamic influences are necessary for the continued production of EEP-LI and are not present in vitro. Alternatively, the dissociation of the cell–cell interactions and/or the accumulation of cell products, particularly pituitary hormones in vitro, may result in a loss of the in vivo paracrine influences or the introduction of factors which inhibit EEP-LI and stimulate TRH-LI. Journal of Endocrinology (1995) 145, 333–341

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Stimulatory effect of thyrotrophin-releasing hormone (TRH) on the release of luteinizing hormone (LH) from rat anterior pituitary cells in vitro

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y83-029 ◽

1983 ◽

Vol 61 (2) ◽

pp. 186-189 ◽

Cited By ~ 3

Author(s):

Noboru Fujihara ◽

Masataka Shiino

Keyword(s):

Luteinizing Hormone ◽

Anterior Pituitary ◽

Pituitary Cells ◽

Thyrotrophin Releasing Hormone ◽

Releasing Hormone ◽

Anterior Pituitary Cells ◽

Lh Release ◽

Lh Rh

The effect of thyrotrophin-releasing hormone (TRH, 10−7 M) on luteinizing hormone (LH) release from rat anterior pituitary cells was examined using organ and primary cell culture. The addition of TRH to the culture medium resulted in a slightly enhanced release of LH from the cultured pituitary tissues. However, the amount of LH release stimulated by TRH was not greater than that produced by luteinizing hormone – releasing hormone (LH–RH, 10−7 M). Actinomycin D (2 × 10−5 M) and cycloheximide (10−4 M) had an inhibitory effect on the action of TRH on LH release. The inability of TRH to elicit gonadotrophin release from the anterior pituitary glands in vivo may partly be due to physiological inhibition of its action by other hypothalamic factor(s).

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Thyroid status affects the regulation of prolactin mRNA accumulation by tri-iodothyronine and thyrotrophin-releasing hormone in cultured rat anterior pituitary cells

Journal of Endocrinology ◽

10.1677/joe.0.1150497 ◽

1987 ◽

Vol 115 (3) ◽

pp. 497-503 ◽

Cited By ~ 9

Author(s):

D. F. Wood ◽

K. Docherty ◽

D. B. Ramsden ◽

K. I. J. Shennan ◽

M. C. Sheppard

Keyword(s):

Anterior Pituitary ◽

Poor Response ◽

Pituitary Cells ◽

Mrna Accumulation ◽

Thyrotrophin Releasing Hormone ◽

Prolactin Synthesis ◽

Prolactin Mrna ◽

In Cells

ABSTRACT The effects of tri-iodothyronine (T3) and TRH on prolactin mRNA accumulation in monolayer pituitary cell cultures prepared from both euthyroid and hypothyroid rats were investigated. Basal prolactin mRNA concentrations and prolactin release into culture medium were increased in hypothyroid cultures, the increase being related to the duration of hypothyroidism in vivo. The inhibitory effects of T3 seen in euthyroid cells were preserved in cells derived from hypothyroid animals, and the degree of inhibition was greater in cells from the most severely hypothyroid rats. However, the stimulation of prolactin synthesis and secretion induced by TRH in euthyroid cultures was not found in the hypothyroid cells. Hypothalamic and anterior pituitary TRH content were measured in similarly hypothyroid and euthyroid rats. A large hypothalamic pool of TRH was found, which was unchanged in hypothyroidism, whereas anterior pituitary TRH content was increased in the hypothyroid rats. The consequent down-regulation of anterior pituitary TRH receptors may explain the poor response of prolactin to TRH seen in vitro. J. Endocr. (1987) 115, 497–503

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Vasopressin as a neuroendocrine regulator of anterior pituitary hormone secretion

Acta Endocrinologica ◽

10.1530/acta.0.1290489 ◽

1993 ◽

Vol 129 (6) ◽

pp. 489-496 ◽

Cited By ~ 33

Author(s):

Andreas Kjær

Keyword(s):

Arginine Vasopressin ◽

Mode Of Action ◽

Anterior Pituitary ◽

Hormone Secretion ◽

Pituitary Hormones ◽

Pituitary Hormone ◽

Anterior Pituitary Hormones ◽

Anterior Pituitary Hormone

Secretion of the anterior pituitary hormones adrenocorticotropin (ACTH), β-endorphin and prolactin (PRL) is complex and involves a variety of factors. This review focuses on the involvement of arginine-vasopressin (AVP) in neuroendocrine regulation of these anterior pituitary hormones with special reference to receptor involvement, mode of action and origin of AVP. Arginine-vasopressin may act via at least two types of receptors: V1− and V2−receptors, where the pituitary V1−receptor is designated V1b. The mode of action of AVP may be mediating, i.e. anterior pituitary hormone secretion is transmitted via release of AVP, or the mode of action may be permissive, i.e. the presence of AVP at a low and constant level is required for anterior pituitary hormones to be stimulated. Under in vivo conditions, the AVP-induced release of ACTH and β-endorphin is mainly mediated via activation of hypothalamic V1− receptors, which subsequently leads to the release of corticotropin-releasing hormone. Under in vitro conditions, the AVP-stimulated release of ACTH and β-endorphin is mediated via pituitary V1b− receptors. The mode of action of AVP in the ACTH and β-endorphin response to stress and to histamine, which is involved in stress-induced secretion of anterior pituitary hormones, is mediating (utilizing V1− receptors) as well as permissive (utilizing mainly V1− but also V2−receptors). The AVP-induced release of PRL under in vivo conditions is conveyed mainly via activation of V1−receptors but V2−receptors and probably additional receptor(s) may also play a role. In stress- and histamine induced PRL secretion the role of AVP is both mediating (utilizing V1 −receptors) and permissive (utilizing both V1− and V2− receptors). Arginine-vasopressin may be a candidate for the PRL-releasing factor recently identified in the posterior pituitary gland. Arginine-vasopressin of both magno- and parvocellular origin may be involved in the regulation of anterior pituitary hormone secretion and may reach the corticotrophs and the lactotrophs via three main routes: the peripheral circulation, the long pituitary portal vessels or the short pituitary portal vessels.

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

International Journal of Toxicology ◽

10.1177/1091581816645797 ◽

2016 ◽

Vol 35 (4) ◽

pp. 463-475 ◽

Cited By ~ 8

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.

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

Endocrinology ◽

10.1210/en.2006-1153 ◽

2007 ◽

Vol 148 (4) ◽

pp. 1736-1744 ◽

Cited By ~ 43

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.

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Prolactin (PRL)-Releasing Peptide Stimulates PRL Secretion from Human Fetal Pituitary Cultures and Growth Hormone Release from Cultured Pituitary Adenomas1

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jcem.86.6.7591 ◽

2001 ◽

Vol 86 (6) ◽

pp. 2826-2830 ◽

Cited By ~ 1

Author(s):

Tami Rubinek ◽

Moshe Hadani ◽

Gad Barkai ◽

Shlomo Melmed ◽

Ilan Shimon

Keyword(s):

Primary Cultures ◽

Pituitary Hormones ◽

Pituitary Cells ◽

Maximal Effect ◽

Dependent Manner ◽

Human Pituitary ◽

Cell Adenoma ◽

In Vitro Effects

The hypothalamic peptide PRL-releasing peptide (PrRP) has recently been cloned and identified as a ligand of an orphan pituitary receptor that stimulates in vitro PRL secretion. PrRP also induces PRL release in rats in vivo, especially in normal cycling females. However, no information on the effects of PrRP in the human is available. To elucidate the role of PrRP in regulating human anterior pituitary hormones, we used human PrRP-31 in primary cultures of human pituitary tissues, including fetal (20–27 weeks gestation) and normal adult pituitaries, as well as PRL- and GH-secreting adenomas. PrRP increased PRL secretion from human fetal pituitary cultures in a dose-dependent manner by up to 35% (maximal effect achieved with 10 nm), whereas TRH was slightly more potent for PRL release. Coincubation with estradiol resulted in enhanced fetal PRL response to PrRP, and GH release was only increased in the presence of estradiol. Although PRL secretion from PRL-cell adenomas was not affected by PrRP, PrRP induced PRL release from cultures of a GH-cell adenoma that cosecreted PRL. PrRP enhanced GH release in several GH-secreting adenomas studied by 25–27%, including GH stimulation in a mixed PRL-GH-cell tumor. These results show for the first time direct in vitro effects of PrRP-31 on human pituitary cells. PrRP is less potent than TRH in releasing PRL from human fetal lactotrophs and is unable to release PRL from PRL-cell adenomas in culture, but stimulated GH from several somatotroph adenomas. Thus, PrRP may participate in regulating GH, in addition to PRL, in the human pituitary.

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Rat anterior pituitary cells in vitro can partly reconstruct in vivo topographic affinities

The Anatomical Record ◽

10.1002/ar.a.10065 ◽

2003 ◽

Vol 272A (2) ◽

pp. 548-555 ◽

Cited By ~ 8

Author(s):

Takahiro Noda ◽

Motoshi Kikuchi ◽

Sachiko Kaidzu ◽

Takashi Yashiro

Keyword(s):

Anterior Pituitary ◽

Pituitary Cells ◽

Anterior Pituitary Cells

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On the role of the peptide galanin in regulation of growth hormone secretion

Acta Endocrinologica ◽

10.1530/acta.0.1250518 ◽

1991 ◽

Vol 125 (5) ◽

pp. 518-525 ◽

Cited By ~ 33

Author(s):

Anna-Lena Hulting ◽

Björn Meister ◽

Lena Carlsson ◽

Agneta Hilding ◽

Olle Isaksson

Keyword(s):

Growth Hormone ◽

Anterior Pituitary ◽

Hormone Secretion ◽

Growth Hormone Secretion ◽

Pituitary Cells ◽

Anterior Pituitary Cells ◽

Human Anterior Pituitary ◽

Plasma Gh

Abstract. The effects of the peptide galanin on growth hormone secretion were studied in vitro using cultured rat and human anterior pituitary cells, and in vivo by iv administration of galanin in both rats and humans. Galanin in concentrations from 10 nmol/l to 1 μmol/l did not alter basal GH release, but slightly inhibited GHRH-stimulated GH release from cultured rat anterior pituitary cells. Galanin (1 μmol/l) did not significantly change basal or GHRH-stimulated GH secretion from cultured human anterior pituitary cells. In contrast, iv injection of 1 μg (300 pmol) galanin to rats induced an increase in plasma GH that was reproducible at repetitive injections. The galanin-induced GH release in rats was of a lower magnitude than the increase in plasma GH after iv injections of GHRH, and was seen with a 5-15 min delay in comparison to iv administered GHRH. In man, iv infusions of galanin (40 pmol ·kg−1 · min−1 · (40 min)) also caused a significant increase in plasma GH, but it occurred 25-30 min after the beginning of the infusion. These results suggest an indirect action of galanin on GH release in both rats and humans, i.e. galanin does not directly affect the somatotropes. In agreement with a central action, no binding sites for galanin could be demonstrated in the rat anterior pituitary by autoradiography. Since galanin did not affect somatostatin release from fragments of rat mediobasal hypothalamus, the stimulatory effects of galanin on GH release are most likely mediated via a stimulatory effect on GHRH neurons.

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Effect of GnRH and its antagonist (Antarelix) on LH release from cultured bovine anterior pituitary cells

Acta Veterinaria Hungarica ◽

10.1556/avet.50.2002.1.10 ◽

2002 ◽

Vol 50 (1) ◽

pp. 79-92 ◽

Cited By ~ 3

Author(s):

Annett Bellmann ◽

F. Schneider ◽

W. Kanitz ◽

Keyword(s):

Anterior Pituitary ◽

Culture System ◽

Gnrh Antagonist ◽

Pituitary Cells ◽

Maximal Effect ◽

Static Culture ◽

Lh Release ◽

Lh Secretion

In the following investigations, the LH secretion of cells from pituitaries in heifers on days 16-18 of their oestrous cycle (n = 14) was analysed. Cells were dissociated with trypsin and collagenase and maintained in a static culture system. For the estimation of LH release, the cells were incubated with various concentrations of mammalian GnRH (Lutrelef) for 6h. To determine the action of Antarelix (GnRH antagonist), the cells were preincubated for 1 h with concentrations of 10-5 or 10-4 M Antarelix followed by 10-6 M GnRH coincubation for a further 6h. At the end of each incubation, the medium was collected for LH analysis. Parallel, intracellular LH was qualitatively detected by immunocytochemistry. Changes in the intensity of LH staining within the cells in dependence of different GnRH concentrations were not observed, but a significant increase LH secretion in pituitary cells was measured at 10-6 M GnRH. Antarelix had no effect on basal LH secretion at concentrations of 10-4 and 10-5 M. After coincubation of pituitary cells with Antarelix and GnRH, Antarelix blocked the GnRH-stimulated LH secretion with a maximal effect of 10-4 M, but the staining of immunoreactive intracellular LH was detected at approximately the same level compared to the pituitary cells treated with exogenous GnRH alone. These data demonstrate that Antarelix is effective in influencing the GnRH-stimulated LH secretion of pituitary cells in vitro. After administration of Antarelix in vivo, the GnRH-stimulated LH secretion of cultured pituitary cells was not inhibited.

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