Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To determine whether galanin (GAL), a 29-amino acid neuropeptide, plays a role in the physiological regulation of the pulsatile secretion of GH and PRL in the male rat, secretory patterns of both hormones were studied in freely moving animals after GAL passive immunoneutralization. Adult male Sprague-Dawley rats were equipped with iv and intracerebroventricular catheters. After 7 days, 3 microliters of a specific GAL antiserum (GAL-AS) or normal rabbit serum (NRS; controls) were infused in the third ventricle of 10 rats, 25 and 1 h before the animals were bled every 15 min for 6 h (1000-1600 h). Plasma GH and PRL concentrations were measured by RIA, and the hormonal secretory patterns were analyzed by the PULSAR program. Control rats, treated with NRS, displayed typical GH secretion, with pulses of high amplitude (167 +/- 27 ng/ml) and low frequency (2.4 +/- 0.2 pulses/6 h), separated by periods of low trough levels (3.8 +/- 0.6 ng/ml). Rats treated with GAL-AS had altered pulsatile GH secretion. Pulse height was markedly reduced (77 +/- 15 ng/ml; P less than 0.01 vs. controls), and peak frequency was higher (3.6 +/- 0.5 pulses/6 h; P less than 0.05), while GH baseline levels and integrated GH secretion over the 6-h sampling period remained unaltered. Injection of rat GH-releasing hormone (1 microgram/rat, iv) caused a similar GH stimulation in both groups of rats, as determined by the peak GH response at 5 min (368 +/- 112 vs. 342 +/- 81 ng/ml) or by the integrated GH response over 1 h (5.13 +/- 1.30 vs. 4.77 +/- 1.15 micrograms.min/ml in NRS- and GAL-AS-treated rats, respectively; P less than 0.05). In contrast to GH, pulsatile secretion of PRL was not affected by the GAL-AS treatment. These results indicate that GAL is a physiological regulator of spontaneous pulsatile secretion of GH, but not PRL, in the male rat. The influence of GAL on GH secretion appears to be exerted within the hypothalamus, mainly by a stimulation of GRF secretion. However, the changes in GH pulse frequency observed after GAL immunoneutralization suggest that GAL might also influence the somatostatin inhibitory tone.
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PMID:Galanin is a physiological regulator of spontaneous pulsatile secretion of growth hormone in the male rat. 168 91

Lactotrophs, somatotrophs, and thyrotrophs have been shown to contain immunoreactive galanin. Furthermore, estrogen stimulates galanin mRNA and peptide levels in the rat anterior pituitary, particularly within lactotrophs. To determine whether galanin is released from the anterior pituitary in a regulated manner, we used cultured pituitary cells from male and ovariectomized Fischer 344 rats implanted with estrogen-containing capsules. Anterior pituitary cells (5 x 10(5) cells/well) were challenged (0.5-3 h) with hypothalamic factors known to regulate anterior pituitary hormone secretion, and medium galanin levels were measured by RIA. In female pituitary cells, galanin secretion was inhibited by dopamine (10 and 100 nM) and stimulated by TRH (20 and 100 nM). Although galanin release was significantly lower in male pituitary cells, dopamine and TRH inhibited and stimulated galanin secretion, respectively. Medium galanin levels were also significantly reduced by somatostatin (5 nM) in both female and male cells. The pattern of PRL release in response to dopamine, TRH, and somatostatin was similar to that observed for galanin, regardless of the sex of the pituitary donor. Although galanin has been localized in somatotrophs, 5 nM GH-releasing hormone (GRF) failed to alter galanin release in male as well as female pituitary cells; GH secretion was significantly increased by GRF. LHRH (5 nM) and CRF (5 nM) failed to alter galanin release in vitro. We conclude that in estrogen-exposed pituitary cells obtained from male and ovariectomized Fischer 344 rats: 1) galanin secretion is inhibited by dopamine and somatostatin, and stimulated by TRH; 2) GRF, LHRH, and CRF do not regulate galanin release in these cells; and 3) the profile of the regulated pathway for galanin release suggests that the primary location of galanin is the lactotroph, probably within secretory granules.
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PMID:Galanin secretion from anterior pituitary cells in vitro is regulated by dopamine, somatostatin, and thyrotropin-releasing hormone. 170 85

Galanin is localized within specific cell types of the rat anterior pituitary gland (AP). Immunocytochemical studies at the light microscope level have shown that lactotrophs, somatotrophs, and thyrotrophs contain galanin in the intact female rat, whereas lactotrophs in the male AP do not. We recently reported that galanin and PRL release from estrogen-treated male and female pituitary cells in culture are coregulated by dopamine, TRH, and somatostatin. This suggested that galanin is stored within secretory granules, conceivably with PRL. Using postembedding immunocytochemistry at the ultrastructural level, the objectives of this study were to: 1) determine the subcellular location of galanin in the AP; 2) elucidate if galanin and PRL are colocalized within the same secretory granules; and 3) compare the cellular localization of galanin in the male and female AP. Male and ovariectomized female (OVEX) Fischer 344 rats were implanted with estradiol-containing or empty Silastic capsules for 2 weeks. Postembedding immunogold labeling was performed using rabbit (for galanin) and guinea pig (for PRL) generated antisera. Two different sizes of colloidal gold spheres were used to localize the hormones in the same tissue section. Galanin was primarily localized in secretory granules of adenohypophyseal cells. Based upon immunocytochemical results and morphological criteria, galanin was contained in somatotrophs but not lactotrophs in the male and OVEX AP. The AP of estrogen-treated rats contained more specific immunogold labeling for galanin than untreated rats. The increased immunoreactivity for galanin was notably associated with lactotrophs. After exposure to estrogen, galanin and PRL were colocalized within the same secretory granules of the male and OVEX pituitary cells. We conclude: 1) galanin is localized within secretory granules of the rat AP; 2) galanin and PRL are colocalized within secretory granules of the male and OVEX AP after estrogen treatment; and 3) galanin is localized in similar cell types in the male and OVEX AP, before and after estrogen treatment. These data provide a morphological basis for the coregulation of galanin and PRL secretion by hypothalamic factors.
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PMID:Colocalization of galanin and prolactin within secretory granules of anterior pituitary cells in estrogen-treated Fischer 344 rats. 171 63

TRH is present in human normal pituitaries and in pituitary adenomas. In this study we demonstrated that the same tissues can release TRH in vitro. Fragments from seven normal pituitaries (10-15 mg/syringe) and dispersed cells from eight prolactinomas, four GH-secreting and two nonsecreting adenomas (1-3 x 10(6) cells/syringe) were perifused using a Krebs-Ringer culture medium. After 1 h of equilibration the perifusion medium was collected every 2 min (1 mL/fraction) for 3 h. TRH, PRL, and GH were measured by RIA under basal conditions and in the presence of 10(-10) to 10(-6) mol/L dopamine (DA), alone or concomitant with haloperidol, or in the presence of 10(-10) or 10(-6) mol/L somatostatin. Both normal pituitary fragments and pituitary adenomatous cells (from all types of adenomas studied) spontaneously released TRH in vitro. TRH was detected in the perifusion medium either immediately after the end of the equilibration period or 30-60 min later. The molecular identity of TRH was assessed by high pressure liquid chromatography. There was no difference in the profile and the rate of TRH secretion between normal and tumoral tissues, and no correlation was found between the level of TRH release and that of PRL or GH secretion. DA stimulated TRH release from normal pituitaries and from PRL- and GH-secreting adenomas at doses as low as 10(-10) mol/L. A concomitant decrease in PRL and GH release was observed from adenomatous cells and in one case of normal tissue. Haloperidol (10(-7) mol/L) antagonized the effect of 10(-8) mol/L DA on both TRH and PRL secretion in normal pituitary and in prolactinomas. DA had no effect on TRH release from two nonsecreting tumors. The amounts of TRH released during 1 h of perifusion were 60-1640 pg/2 mg wet wt tissue in normal pituitaries and 54-2174 pg/10(6) cells in adenomas; these values were very high compared to those precedently reported within the tissues. These results indicate that pituitary cells can release TRH in vitro and suggest that TRH might be synthesized in situ. We suggest that TRH could act on pituitary hormone secretion and/or cell proliferation via a paracrine and/or an autocrine mechanism.
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PMID:Normal and adenomatous human pituitaries secrete thyrotropin-releasing hormone in vitro: modulation by dopamine, haloperidol, and somatostatin. 197 64

Interleukin-6 (IL-6) is an inflammatory cytokine that stimulates T-cell activation and B-cell differentiation. We recently reported that picomolar concentrations of IL-6 stimulated PRL, GH, and LH release in vitro. These data suggested that IL-6 may function as a hypothalamic releasing factor for anterior pituitary hormones. Medial basal hypothalami (MBH) were incubated for 60-90 min in Krebs-Ringer bicarbonate buffer supplemented with 0.025% BSA, and the conditioned medium was assayed for IL-6 concentrations by the 7TD1 cell growth factor assay. It was found that MBH released IL-6 in vitro. Although depolarizing concentrations of K+ (56 mM) did not increase IL-6 release, somatostatin release from the MBH was increased significantly. The bacterial endotoxin lipopolysaccharide (LPS; 1-100 ng/ml) induced significant increases in IL-6 release from the MBH. The presence of IL-6 in the hypothalamus suggested a possible role for this cytokine in the regulation of neuropeptide release; however, the release of somatostatin was not affected by 20 ng/ml IL-6. Comparison studies of neural and neuroendocrine tissues revealed that the anterior and posterior pituitaries released larger amounts of bioactive IL-6 than the MBH or parietal cortex during a 4-h incubation; induction of IL-6 release by endotoxin occurred only in the anterior pituitary and hypothalamus. IL-6 mRNA was detectable in the MBH and anterior pituitary tissue after a 4-h incubation; however, no IL-6 mRNA was detectable in freshly isolated tissues. LPS (100 ng/ml) and (Bu)2cAMP (1 mM) increased IL-6 mRNA accumulation in and IL-6 release from the MBH and anterior pituitary. These data suggest that the MBH synthesizes and releases IL-6 via a nonneuronal source in vitro.
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PMID:Endotoxin-induced release of interleukin-6 from rat medial basal hypothalami. 197 93

The medical treatment of acromegaly with dopaminergic drugs has its physiopathological premise in the observation that agents capable of stimulating dopaminergic receptors directly are capable of determining GH secretion inhibition in a large percentage of acromegalic patients. Chronic administration of 5-20 mg/die of bromocryptin, long acting dopaminergic agonist, leads to a stable reduction in the levels of GH and somatomedin C (SmC) in about 50% of patients. However, these are only normalised in 20%. Treatment induces marked improvement in the clinical and metabolic changes typical of acromegalic disease. The therapeutic effect of dopaminergics may be maintained for periods of treatment lasting years but upon suspension of treatment pH levels return quickly to pretreatment levels. The antitumoral effect of the dopaminergic frequently encountered in prolactinomas is a rarer event in acromegaly and occurs more readily in patients with mixed secreting GH and PRL tumours than in pure GH. Currently octractide, a long lasting somatostatin analogue, is the most effective drug in the medical treatment of acromegaly; however the dopaminergic agonists remain a valid alternative.
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PMID:[Medical treatment of acromegaly with dopaminergic agents]. 198 Mar 33

A total of 79 consecutive patients with pituitary tumours were screened for multiple endocrine neoplasia type 1 (MEN-1). The 79 patients included 21 patients with acromegaly, nine with Cushing's disease, 18 with prolactinomas, three with mixed pituitary adenomas (GH and PRL), and 28 patients with no detectable hypersecretion of hormones. The screening consisted of: (1) a family history, (2) a uniform medical history of the patient using a standard questionnaire, and (3) hormonal evaluation including measurements of the serum levels of insulin, gastrin, glucagon, somatostatin, vasoactive intestinal polypeptide and pancreatic polypeptide. Ionized calcium and glucose concentration in serum were also measured. We found no patients with the MEN-1 syndrome. In one patient, we found a transient elevation of serum concentrations of pancreatic polypeptide for which we have no explanation. In another patient, the serum gastrin concentration was elevated secondary to achlorhydria. No other endocrine disorders were found, and no patients had relatives with recognized endocrine pancreatic tumours, primary hyperparathyroidism (HPT), or pituitary adenomas.
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PMID:Screening for multiple endocrine neoplasia type 1 in patients with recognized pituitary adenoma. 198 64

It has long been known that endogenous pyrogen, released as a result of injection of typhoid vaccine or in response to infection, produces fever and increases ACTH secretion. Recent studies have indicated that endogenous pyrogen is, at least in part, IL-1. This monokine has now been shown to activate the release of ACTH by a hypothalamic mechanism with release of CRF and possibly vasopressin, which stimulates the corticotrophs. There may also be a pituitary action to stimulate the release of ACTH directly. In our experiments we showed that IL-1 at low but not higher doses appears to act intrahypothalamically to stimulate GH and PRL release and to inhibit TSH release. In the meantime, another monokine, cachectin, was isolated and its structure determined. We have found that this monokine can act following its third ventricular injection to stimulate ACTH, PRL, and GH release and to inhibit TSH release, at least in part, by release of prostaglandins since indomethacin, an inhibitor of prostaglandin synthesis, produced a blockade of the responses except for those of ACTH. This peptide also has highly potent effects to alter pituitary hormone release by direct action on the pituitary to stimulate ACTH, GH, and TSH and to a slight extent PRL release. These actions appear to involve prostaglandins since indomethacin blocks all of the effects except for the effect on ACTH secretion. This monokine also produces a dose-related lowering of anterior pituitary cyclic AMP levels. When the monokine was incubated along with somatostatin, the lowering of cyclic AMP was reversed, and a potent PRL-releasing effect of the monokine was visible. We have begun studies with a third monokine, gamma interferon, which indicate that it stimulates ACTH release but suppresses plasma GH and TSH levels by a hypothalamic action. It is apparent that these various monokines have powerful effects to alter hypothalamic-pituitary function and that they probably mediate most of the effects of infections on the release of anterior pituitary hormones.
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PMID:Role of monokines in control of anterior pituitary hormone release. 223 30

17 beta-Estradiol (E2) alters different functions of pituitary cells, including cell sensitivity to several neurohormones such as LHRH, TRH, somatostatin, or dopamine, presumably by affecting receptor coupling mechanisms. Attempting to pinpoint the membrane processes underlying this modulation, we studied the effect of E2 on pituitary kinase-C (PKC) activity, a major signal transduction enzyme. The distribution of calcium- and phospholipid-dependent partially purified PKC (chromatography on DEAE-52 cellulose columns) was evaluated in membrane and cytosol fractions from anterior pituitaries of ovariectomized (OVX) or OVX plus E2-treated rats. E2 administration by implants to OVX animals increased significantly both soluble and particulate enzyme activity. The effect increased progressively from 24 h to 5 days after E2 treatment. Administration of 17 alpha-estradiol, an inactive stereoisomer of E2, was ineffective, pointing to stereospecific interaction. Total destruction of neural connections to the pituitary (complete hypothalamic lesions) did not modify the enzyme response to E2 administration, indicating a direct effect of the steroid on pituitary PKC activity. A direct E2 (10(-9) M) effect was confirmed in primary mixed cultures of pituitary cells; it was time dependent (15-96 h) and specific, and reflects a genomic E2 action. E2 treatment for shorter times had no effect on the enzyme levels or the membrane redistribution of PKC activity. In contrast, under the same experimental conditions phorbol esters (12-O-tertadecanoyl-phorbol-13-acetate (TPA] induced a rapid and sustained translocation of the enzyme. PKC activity was found in all pituitary cell types, with maximal activity in fractions of gonadotropes and thyrotropes, as evaluated in cultures enriched in certain types of pituitary cells separated by means of unit gravity gradient sedimentation. E2 treatment (10(-9) M; 72 h) significantly increased both soluble and particulate enzyme levels in all cell types. In addition, administration of E2 (10(-9) M; 72 h) to cell cultures strongly increased the TPA-evoked LH and PRL release. These results indicate that E2-induced changes in pituitary function include selective effects of the steroid on PKC activity involved at different levels in the coupling mechanisms.
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PMID:Estradiol modulates protein kinase C activity in the rat pituitary in vivo and in vitro. 229 3

The hypothalamic peptide somatostatin (SRIF) suppresses secretory activity in phenotypically distinct pituitary endocrine cells. We have used tight-seal whole-cell recording techniques to study the peptide's effects on the electrical properties of tumor pituitary cells derived from rat (GH3/B6) and human adenomas that secrete human PRL in a SRIF-sensitive manner. Both cell types exhibited qualitatively similar electrophysiological properties and electrical responses to SRIF. Under the experimental conditions employed the majority of cells spontaneously generated Ca2+-dependent actions potentials. The actions of the peptide on cellular excitability were markedly affected by the presence of horse and fetal calf sera. Without these additives the electrical responses faded and could not be studied in detail. Therefore, recordings were conducted in media containing sera. In the presence of sera almost all cells spontaneously generated Ca2+ action potentials, and peptide-induced changes in excitability were well preserved. SRIF depressed spontaneous and evoked action potential activity in a dose-dependent manner at concentrations that reduced intracellular free calcium ([Ca2+]i) and suppressed basal PRL release. Current and voltage clamp experiments revealed coordinate actions of the peptide on excitable membrane properties. SRIF (1 nM) enhanced a depolarization-activated, rapidly inactivating outward K+ current, thereby effectively reducing the rate at which action potentials occurred. Over the 10-1000 nM range SRIF slowly activated a virtually noninactivating K+ conductance over a wide range of membrane potential. This effectively hyperpolarized cells away from the threshold for triggering Ca2+-dependent action potentials and shunted the membrane. The peptide induced K+ conductance activated at the level of the resting potential was progressively lost during the intracellular dialysis of whole-cell recording. Dilute aqueous lysates of cells included in the patch pipette prevented much of the rundown of this SRIF-induced electrical response while inclusion of an ATP-regenerating system preserved some of the peptide action. Over the 10-100 nM concentration range SRIF also reduced voltage-dependent Ca2+ current. Furthermore, pretreatment of cells with pertussis toxin abolished SRIF action on cellular excitability, suggesting that SRIF can regulate the function of ionic channels through GTP-binding proteins (G proteins). The results demonstrate that SRIF acts coordinately on the primary conductances expressed in tumor PRL cells to attenuate or block Ca2+ action potential generation and thus Ga2+ entry from extracellular sources.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Somatostatin blocks Ca2+ action potential activity in prolactin-secreting pituitary tumor cells through coordinate actions on K+ and Ca2+ conductances. 245 3


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