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)

Ectopic GHRH is a relatively uncommon cause of acromegaly, which should be differentiated from pituitary adenoma, in order to avoid damage to the pituitary gland from unnecessary interventions. We report here on a 66-year-old man with acromegaly due to a GHRH-secreting bronchial carcinoid tumour, who recovered completely following removal of the tumour. His hormonal status was studied before and after the operation. Basal GH, GHRH, IGF-I and PRL levels, as well as plasma GH response to glucose load and TRH administration were abnormal before the operation, and became normal thereafter. The somatostatin analogue SMS 201-995 was found to be a potent inhibitor of the ectopic GHRH and the GH secretion (greater than 500 to 42 ng/l and 15.4 micrograms/l to 0.8 microgram/l, respectively). The effect on GHRH proved to be due to direct effect of somatostatin on the tumour cells, as demonstrated in tissue culture studies. A mixed meal was found immediately to suppress GHRH levels without such an effect on GH secretion. We conclude that the neuroendocrine tests usually practised in acromegaly cannot differentiate between ectopic GHRH secretion and pituitary adenoma. High plasma GHRH levels may serve as a diagnostic test for excessive GHRH production, which is almost always ectopic. These high levels are suppressible by somatostatin and a mixed meal.
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PMID:Acromegaly due to ectopic growth hormone-releasing hormone secretion by a bronchial carcinoid tumour. Dynamic hormonal responses to various stimuli. 168 1

We have investigated the regulation of mRNA levels of alpha- and beta-subunits of guanine nucleotide-binding regulatory proteins (G proteins) by peptide hormones in prolactin producing rat pituitary adenoma cells (GH3 cells) in culture. The cells were treated with thyroliberin (1 microM), vasoactive intestinal peptide (1 microM) or somatostatin (10 microM) for 6 to 48 hours. Thyroliberin and vasoactive intestinal peptide increased the levels of Gs alpha Go alpha, Gi-2 alpha, Gi-3 alpha, Gx alpha, G beta 36 and mRNAs. The effect of vasoactive intestinal peptide was however earlier and more pronounced. Gi-2 alpha mRNA levels showed the quantitatively largest alterations. Somatostatin upregulated Gs alpha and downregulated Go alpha and Gi-2 mRNAs. G protein mRNAs for Gi-2 alpha and Go alpha were increased by exposure of the cells to a medium devoid of serum. We conclude that G protein mRNA levels are subjected to alterations by hormones that act through the corresponding G proteins in the regulation of prolactin synthesis and secretion.
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PMID:Regulation of G protein mRNA levels by thyroliberin, vasoactive intestinal peptide and somatostatin in prolactin-producing rat pituitary adenoma cells. 168 38

The effects of hypothyroidism duration on several factors implicated in GH secretion control were studied in the male rat at different maturity stages, ranging from the peripuberal period to adulthood. Thyroid ablation was performed on 22-day-old Wistar male rats maintained on a low iodine diet (T group). Age-paired controls (C group) were fed with the same diet, supplemented with potassium iodide. Subgroups of T and C animals (aged 32, 42, 52, 82 and 112 days) were studied 10, 20, 30, 60 and 90 days after surgery. After pentobarbital anesthesia, jugular blood was withdrawn before and 5 min after an intravenous TRH stimulus, for GH assay. Hypothalamic and pituitary tissues were obtained in order to measure GH, immunoreactive somatostatin (IR-SRIF) and growth hormone-releasing factor (IR-GRF). Growth rate and serum testosterone confirmed that C rats reached sexual maturity by day 30 of the study. Mean +/- SE serum GH (ng/ml) increased (p less than 0.05) in C animals from day 10 (38.5 +/- 5) to day 30 (67.4 +/- 7.3), with no significant variations thereafter. The same time sequence pattern was observed in pituitary GH concentrations. In T rats, both serum and pituitary GH decreased progressively from day 10 to 90, being significantly lower than in C at all times of the study. No GH response to TRH could be found in C groups. In contrast, GH increased significantly (p less than 0.05) in T animals after TRH at days 20 and 30.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Influence of hypothyroidism duration on developmental changes in the hypothalamic factors implicated in growth hormone secretion in the male rat. 168 42

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

In experiments using fetal rat liver cultured cells TRH was shown to stimulate total protein synthesis but not RNA synthesis during long incubation. Somatostatin affected neither protein synthesis nor RNA synthesis in cultured liver cells. Possible physiological role of peripheral TRH during perinatal period in the rat is discussed.
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PMID:[The direct stimulating action of thyroliberin on the biosynthesis of total protein in cultured liver cells of rat fetuses]. 171

There was no apparent difference in the regional distribution of neuropeptides in the brain of male and female rats. The highest levels of immunoreactive leu-enkephalin, TRH, substance P and somatostatin were found in the hypothalamus, while the striatum and the cerebral cortex had the highest concentrations of met-enkephalin and cholecystokinin respectively. The lowest concentrations of these were found in the cerebellum. Enkephalins (cerebral cortex), substance P (cerebral cortex and brain stem), and somatostatin (brain stem and striatum) showed higher level in the female while enkephalin and substance P contents in the anterior pituitary were higher in the male.
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PMID:The regional distribution of thyrotropin releasing hormone, leu-enkephalin, met-enkephalin, substance P, somatostatin and cholecystokinin in the rat brain and pituitary. 171 78

This paper analyses the effect of hypothyroidism on pancreatic TRH and somatostatin concentrations, as well as the action of exogen TRH on pancreatic amylase secretion from isolated lobules and dissociated acini of both healthy and hypothyroid rats. In the hypothyroid group, pancreatic TRH and somatostatin increased. In the pancreatic lobules of untreated animals, bethanechol produced stimulatory action that was inhibited by TRH. On the other hand, lobules from hypothyroid rats did not respond to bethanechol stimulation. Acini amylase secretion after bethanechol stimulation was similar in both groups, although hypothyroid animals were more sensitive to the inhibitory effect of TRH. These findings suggest the existence of a factor blocking the amylase secretion in pancreatic lobules. This agent, probably TRH, could be eliminated in the experimental model of dissociated acini.
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PMID:Different secretory response of pancreatic isolated lobules and dissociated acini from hypothyroid rats to exogen TRH. 171 66

The release of pituitary GH appears to be critically dependent on alterations in the free intracellular Ca2+ concentration ([Ca2+]i). However, little is known about the nature of Ca2+ signalling within normal pituitary cells. We, therefore, examined [Ca2+]i patterns in individual cultured pituicytes of adult male rats under basal conditions and in response to GH regulatory agents, using the calcium-sensitive dye fura-2 together with digital imaging microscopy. Perfusion of cultured anterior pituitary cells with GH-releasing factor (GHRF) resulted in a marked increase in [Ca2+]i in specific pituitary cells. These cells did not respond to other hypothalamic secretagogues (GnRH, TRH, or CRF), and there was no evidence of desensitization on repetitive administration of GHRF. Somatotrophs (n = 134) exhibited spontaneous oscillations of [Ca2+]i in the basal state, with considerable heterogeneity of oscillatory patterns among cells. After application of a near-maximal stimulatory dose of GHRF (1 nM), there was a striking 2.2-fold increase in the amplitude of [Ca2+]i oscillations and only a modest increase in their frequency. Forskolin (1 microM) augmented somatotroph [Ca2+]i in patterns similar to those of GHRF. Somatostatin (10 nM) abolished the [Ca2+]i response to GHRF (n = 26); this reflected a marked reduction in the amplitude of [Ca2+]i oscillations and a slight reduction in their frequency. Ca(2+)-free medium or the Ca2+ channel antagonist nimodipine (0.1-1 microM) suppressed the Ca2+ stimulatory effect of GHRF. Conversely, the Ca2+ channel agonist BAY K8644 (1 microM) strikingly augmented the GHRF-induced rise in [Ca2+]i, with a major stimulatory effect on the amplitude of [Ca2+]i oscillations and no observed effect on their frequency. In summary, GHRF and other hypothalamic secretagogues increase [Ca2+]i in pituitary cells in a highly specific manner, consistent with the known specificity of their effects on hormone release. Somatotrophs exhibit spontaneous rhythmic oscillation of [Ca2+]i in the basal state. Known regulators of GH release markedly alter the [Ca2+]i oscillatory pattern in characteristic manners, exerting predominant effects on the amplitude of [Ca2+]i pulses and lesser effects on their frequency. These striking effects of GH regulatory agents on pituitary Ca2+ signalling are consistent with the concept that modulation of [Ca2+]i is a critical mediator of somatotroph function.
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PMID:Calcium signalling in single growth hormone-releasing factor-responsive pituitary cells. 173 36

An invasive TSH-secreting adenoma inducing mild hyperthyroidism was diagnosed in a 16-year-old male. Initial surgical treatment led to a temporary clinical and biological improvement. Recurrence of the thyrotoxicosis was treated with the somatostatin analogue, SMS 201-995 (octreotide) with normalization of the serum thyroid hormone levels with a dose of 200 micrograms per day. With immunoelectron microscopy, the tumour cells appeared poorly granulated with small secretory granules located at the periphery of the cells; only part of those were immunoreactive with an anti-TSH beta monoclonal antibody. No specific TRH binding site was found in a tumour membrane preparation. By quantitative autoradiography, somatostatin specific binding sites were as numerous in the TSH-secreting tumour as in control GH-secreting tumours. Binding kinetics and guanosine triphosphate dependency of the binding were equivalent in the TSH and GH tumours tested. Although all of the tumour cells displayed the same ultrastructural features, some were non-immunoreactive, suggesting that they could secrete an altered form of TSH. The absence of TRH receptors in the tumour cells is in accordance with previous reports on this type of tumour. We confirm the efficiency of octreotide treatment in this case of neoplastic TSH inappropriate secretion. The therapeutic effect of octreotide goes along with the presence of a high density of guanine nucleotide-dependent somatostatin binding sites in the tumour cells.
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PMID:A human TSH-secreting adenoma: endocrine, biochemical and morphological studies. Evidence of somatostatin receptors by using quantitative autoradiography. Clinical and biological improvement by SMS 201-995 treatment. 185 93


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