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)

The effects of streptozotocin-induced diabetes on pituitary growth hormone (GH) content and release from incubated pituitaries were investigated. Male rats were made diabetic by a single injection of streptozotocin (65 mg/kg) and sacrificed by decapitation 15 days later. Pituitary GH concentration was significantly reduced in streptozotocin diabetic rats as compared to that observed in control animals. The amount of GH released from hemipituitaries was also lower in diabetic rats than in controls. Kinetic characteristics of somatostatin (SRIF) inhibition of GH release were not affected by the treatment. These results suggest that the decrease in plasma GH observed by some investigators in streptozotocin diabetic rats is probably due to a deficiency in GH storage and/or synthesis rather than a change in the responsiveness of pituitary GH cells to SRIF.
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PMID:Influence of streptozotocin-induced diabetes on growth hormone secretion in the rat. 613 72

Growth hormone (GH) secretion was studied in children after a single small intravenous (i.v.) dose of somatostatin (Somatotropin Release Inhibiting Factor, SRIF). After a short decrease of the GH level there was a slow increase culminating at 60 minutes, then again a decrease with the lowest point at 90 minutes. During the third hour the GH level showed a second peak; this was more frequent than the first one. It is concluded that a single small dose of somatostatin during the third hour after its administration can cause an increase of the GH level.
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PMID:Changes of the growth hormone level after a single small dose of somatostatin. 613 27

Female rats bearing N-nitrosomethylurea-induced mammary carcinomas were treated with pergolide mesylate to suppress serum prolactin. The drug was given alone, or with somatostatin, 20 micrograms/hr delivered by osmotic minipump for 7 days to suppress serum growth hormone. Tumour regressions did not occur with pergolide alone, but did so promptly in all of 5 rats when growth hormone levels were also suppressed by somatostatin. A potent long-acting agonistic analogue of somatostatin, L362,823 produced similar tumour regressions at a dose of 5 micrograms/hr when given with pergolide, but was ineffective alone. This dose completely prevented the episodic release of pituitary growth hormone.
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PMID:Rat mammary carcinoma regressions during suppression of serum growth hormone and prolactin. 613 74

The effect of physiological elevation of growth hormone levels on ketone body kinetics was determined using a 14C-ketone body tracer technique in normal and acutely insulin-deficient man. Changes of ketone body production and metabolic clearance rates during growth hormone infusion (plasma levels of approximately 25 micrograms/1) were measured during basal conditions and during heparin-induced elevation of non-esterified fatty acid levels. Growth hormone administration to six subjects fasted overnight resulted in an increase in ketone body production which exceeded that observed in nine control subjects (5.5 +/- 0.5 versus 3.1 +/- 0.1 mumol X kg-1 X min-1, p less than 0.025) after elevation of plasma non-esterified fatty acids. Growth hormone infusion increased glycerol and non-esterified fatty acid concentrations indicating enhanced lipolysis. During somatostatin-induced acute insulin deficiency (n = 7), growth hormone enhanced the increase in total ketone body production observed in six subjects receiving somatostatin alone (8.4 +/- 0.8 versus 4.1 +/- 0.7 mumol X kg-1 X min-1, p less than 0.01). Total ketone body metabolic clearance decreased by 50% during somatostatin and remained uninfluenced by growth hormone. Non-esterified fatty acids and glycerol levels increased during somatostatin, and growth hormone failed to alter non-esterified fatty acid levels significantly. The results demonstrate a stimulatory effect of high physiological growth hormone levels on ketogenesis which is largely explained by an enhancement of lipolysis and thus increase in substrate supply for ketogenesis. Growth hormone administration during acute insulin deficiency enhanced ketogenesis in the absence of alterations in plasma non-esterified fatty acid levels, suggesting a direct hepatic ketogenic effect.
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PMID:Effect of physiological elevation of plasma growth hormone levels on ketone body kinetics and lipolysis in normal and acutely insulin-deficient man. 614 2

The pituitary growth hormone (GH) response to the growth hormone-releasing factor, hpGRF-44, was evaluated in male rats with various lesions of the central nervous system. These included an electrical lesion of the ventromedial hypothalamus, a chemical lesion of the arcuate nucleus induced by neonatal treatment with monosodium glutamate, a functional lesion of catecholamine synthesis with alpha-methyl-p-tyrosine or a functional lesion of catecholamine storage with reserpine. The first three lesions appear to partially inhibit normal somatostatin secretion since in every instance hpGRF-44 administration induced a significant increase in plasma GH concentrations. In contrast, reserpine blocked the GH response to hpGRF-44, presumably by stimulating somatostatin secretion. The pituitary GH response to hpGRF-44 in the above described models was enhanced by pretreatment of the rats with antibodies against somatostatin. The pituitary GH response to repeated injections of hpGRF-44 was also evaluated in rats with an anatomical lesion of the arcuate nucleus or a functional lesion of catecholamine synthesis. The maximum GH response did not vary over time to the repeated injections of hpGRF-44 in rats with lesions of the arcuate nucleus; however, interruption of catecholamine synthesis resulted in a significant decrease in the GH response to hpGRF-44 over time.
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PMID:Pituitary response to growth hormone-releasing factor in rats with functional or anatomical lesions of the central nervous system that inhibit endogenous growth hormone secretion. 614 44

Somatostatin is a14-amino acid peptide hormone that inhibits the secretion of a variety of other polypeptide hormones, including growth hormone. Here we describe an experimental system used to determine whether somatostatin can discriminate in its inhibition between secretory and plasma membrane proteins. Growth hormone-secreting cells (GH3) were infected with vesicular stomatitis virus and pulse-chased with [35S]methionine to follow the simultaneous intracellular transit of growth hormone and the viral membrane glycoprotein, G protein. Secretion of growth hormone was monitored by immunoprecipitation of chase media, while appearance of G protein on the plasma membrane was detected by cell surface labeling and virus purification. In the presence of somatostatin (10 micrograms/ml), the secretion of growth hormone was inhibited by 80%. In contrast, G protein appeared on the plasma membrane with slightly enhanced kinetics. When cells were treated with the ionophore monensin (0.2 microM), there was a dramatic inhibition of both the secretion of growth hormone and the incorporation of G protein into plasma membranes. Our results on the differential effect of somatostatin provide evidence for sorting of secretory and membrane proteins into distinct compartments in the secretory pathway. The data further suggest that this sorting event occurs late in the Golgi complex or after proteins exit from that organelle.
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PMID:Somatostatin discriminates between the intracellular pathways of secretory and membrane proteins. 614 20

Growth hormone (GH) secreting cells direct complement-mediated plaque formation (clear zones of hemolysis surrounding the somatotropes) in mixed pituitary cell cultures incubated as a monolayer with protein-A coupled ovine erythrocytes (oRBC) in the presence of GH antiserum. Plaques were maximal in number after 4 h; growth hormone-releasing hormone (GHRH) and somatostatin increased and decreased, respectively, the rate of formation of plaques and their final sizes. Approximately 30% of all pituitary cells formed GH plaques and a similar fraction stained for GH using peroxidase-antiperoxidase immunocytochemistry (ICC). The plaque areas of individual somatotropes (reflecting the amount of GH released) covered a 20-fold range from the smallest to the largest in the 3 treatment groups. Somatostatin-treated and untreated cells formed frequency distributions of plaque sizes that were unimodal. In contrast, GHRH produced a bimodal frequency distribution suggestive of a sub-population of somatotropes preferentially responsive to this secretagogue. This new assay coupled with other morphological and biochemical techniques that can be applied to single cells will permit further analysis of these sub-populations of somatotropes.
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PMID:A reverse hemolytic plaque assay for microscopic visualization of growth hormone release from individual cells: evidence for somatotrope heterogeneity. 615 Nov 29

Growth hormone (GH) is a protein hormone produced by the somatotrophs of the anterior pituitary gland of birds and other vertebrates. The secretion of GH in birds is under hypothalamic control; it involves three peptidergic releasing factors: growth hormone-releasing factor (GRF) (stimulatory); thyrotropin-releasing hormone (TRH) (stimulatory); and somatostatin (SRIF) (inhibitory). In addition, there is evidence for effects of biogenic amines (including serotonin and norepinephrine) and prostaglandins at the level of the hypothalamus and possibly also the pituitary gland. In all avian species examined, plasma concentrations of GH are high in young posthatching chicks but low in the adult and embryo. The difference in plasma concentrations of GH between young and adult birds is due to both greater GH secretion and reduced clearance. The lower secretion of GH in adult birds reflects fewer somatotrophs in the pituitary, changes in somatotroph structure, and reduced GH responses to TRH or GRF administration. There is only limited data on the role of GH in birds. GH appears to be required for normal growth; acting at least in part by increasing somatomedin production. However, plasma concentrations of GH do not necessarily correlate with growth rate. For instance, in chicks with reduced growth rate owing to either goitrogen or protein deficiency in the diet, plasma concentrations of GH are elevated. GH also can influence lipid metabolism by increasing lipolysis, decreasing lipogenesis, and stimulating the uptake of glucose by adipose tissue. The physiological significance of these actions is, however, not established. In addition, GH affects the secretion of other hormones, the immune system, and perhaps also the reproductive system.
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PMID:Growth hormone: its physiology and control. 615 79

Growth hormone (GH)-releasing activity has been detected in extracts of carcinoid and pancreatic islet tumors from three patients with GH-secreting pituitary tumors and acromegaly. Bioactivity was demonstrated in 2 N acetic acid extracts of the tumors using dispersed rat adenohypophyseal cells in primary monolayer culture and a rat anterior pituitary perifusion system. The GH-releasing effect was dose responsive and the greatest activity was present in the pancreatic islet tumor. Small amounts of activity were also found in two other tumors (carcinoid and small cell carcinoma of lung) unassociated with GH hypersecretion. Each of the tumors contained somatostatin-like immunoreactivity but the levels did not correlate with the net biologic expression of the tumor. Sephadex G-75 gel filtration indicated the GH-releasing activity to have an apparent molecular size of slightly greater than 6,000 daltons. The GH-releasing activity was adsorbed onto DEAE-cellulose at neutral pH and low ionic strength, from which it could be eluted by increasing ionic strength. The GH-releasing activity was further purified by high pressure liquid chromatography using an acetonitrile gradient on a cyanopropyl column to yield a preparation that was active at 40 ng protein/ml. Partially purified GH-releasing activity, from which most of the bioactive somatostatin had been removed, increased GH release by pituitary monolayer cultures to five times base line. Enzymatic hydrolysis studies revealed that the GH-releasing activity was resistant to carboxypeptidase, leucine-aminopeptidase, and pyroglutamate-amino-peptidase but was destroyed by trypsin and chymotrypsin, indicating that internal lysine and/or arginine and aromatic amino acid residues are required for biologic activity and that the NH2-terminus and CO9H-terminus are either blocked or not essential. The results provide an explanation for the presence of GH-secreting tumors in some patients with the multiple endocrine neoplasia syndrome, type I, and warrant the addition of GH-releasing activity to the growing list of hormones secreted by tumors of amine precursor uptake and decarboxylation cell types.
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PMID:Partial purification and characterization of a peptide with growth hormone-releasing activity from extrapituitary tumors in patients with acromegaly. 624 40

Growth hormone-secreting human pituitary adenoma cells in long-term culture show a decline in GH secretion. We investigated the effects of dexamethasone on GH production and on the responsiveness of the adenoma cells to various drugs. Twenty-four-hour GH secretion by cultures from seven acromegalics was consistently stimulated by 100 nM-dexamethasone. In four out of seven cultures the effect of dexamethasone occurred within 24 h. After 3 weeks in culture the decline in GH secretion by control cultures was over 90%, while in dexamethasone-treated cultures this was limited to less than 50%. The effect of dexamethasone was dose-dependent over a range of 1 nmol/l to 10 mumol/l. Dexamethasone stimulated not only GH secretion (fivefold), but also GH content (twofold). Cycloheximide and actinomycin D blocked the stimulatory effect of dexamethasone on GH secretion, the latter irreversibly. After 4 days of treatment with 100 nM-dexamethasone, the relative effects of somatostatin, prostaglandin E1, bromocriptine and thyrotrophin releasing hormone were the same in treated and untreated cultures. However, the response to synthetic GH releasing factor (GRF) was greatly enhanced by pretreatment of adenoma cells with dexamethasone (100 and 5 nmol/l). Cells unresponsive to small concentrations of GRF could be stimulated effectively by GRF after pretreatment with dexamethasone.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Human growth hormone-secreting pituitary adenoma cells in long-term culture: effects of dexamethasone and growth hormone releasing factor. 642 77


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