UNIPROT:P61278 - FACTA Search

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Query: UNIPROT:P61278 (somatostatin)
22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Somatostatin (SRIF)-like immunoreactivity (SLI) in the thyroid glands of human and several animal species were compared, and the SLI peptides were characterized chromatographically and immunologically. All specimens were extracted with 2 M acetic acid, and the SLI content determined by RIA. The SLI concentrations in guinea pigs [34.3 +/- (SE) 4.8 ng/mg protein] and rabbits (9.4 +/- 0.8 ng/mg protein) were much greater than those in other mammals: dogs, rats, mice, and humans. On gel filtration of extracts of the guinea pig, rabbit and dog thyroids, the major peak of SLI (1.6 K SLI) coeluted with synthetic SRIF-14 (S-14). Two other forms of SLI ("big" SLI and 3 K SLI) were also detected, although their relative proportions to total SLI were small (2.3 to 8.2%). The 3 K SLI and 1.6 K SLI from guinea pig and rabbit thyroids contained peptides coeluting with synthetic SRIF-28 (S-28) and S-14, respectively, on reverse-phase high performance liquid chromatography. The dilution curves of the two molecular forms of SLI, i.e. 3 K SLI and 1.6 K SLI, were parallel to the displacement curves of S-28 and S-14 in the SRIF RIA. It is concluded 1) that the thyroid contents of SLI varied greatly from species to species, with the highest content being found in guinea pig thyroids; 2) that in guinea pigs, rabbits, and dogs, the predominant form of thyroid SLI is 1.6 K SLI; and 3) that the 3 K SLI and 1.6 K SLI peptides from guinea pig and rabbit thyroids are immunologically and chromatographically indistinguishable from S-28 and S-14, respectively.
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PMID:Somatostatin-like immunoreactivity in mammalian thyroid glands: contents and partial characterization. 614 31

Tryptophan is readily oxidized to oxindolylalanine (2-hydroxytryptophan) in good yield on treatment in acetic acid solution with a mixture of dimethyl sulfoxide (DMSO) and concentrated aqueous HCl at room temperature. Other sulfoxides can be used in combination with HCl; for example, methionine sulfoxide reacts with an equimolar amount of tryptophan to give high yields of methionine and oxindolylalanine. Methionine and cysteine are quantitatively oxidized by DMSO/HCl to methionine sulfoxide and cystine, respectively. The tryptophan containing peptides LRF (luteinizing hormone-releasing factor), somatostatin, valine-gramicidin A and ACTH 1-24 were each treated with the DMSO/HCl reagent in acetic acid solution and the corresponding oxindolylalanine-derivatives isolated in over 90% yield after chromatography. The identity and purity of the derivatives were established on the basis of ultraviolet spectral characteristics and quantitative amino acid analysis of the oxindolylalanine content of acid hydrolyzates of the oxidized peptides with 3N-p-toluenesulfonic acid at 110 degrees for 24 h. The results indicate that modification of tryptophan peptides with DMSO/HCl provides a useful procedure, which seems superior to previously used reagents. In addition, the method could be well applied to other indoles of biological and pharmacological interest.
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PMID:Oxidation of tryptophan to oxindolylalanine by dimethyl sulfoxide-hydrochloric acid. Selective modification of tryptophan containing peptides. 615 58

The role of various bioactive peptides in the control of secretion of hypothalamic somatostatin into the hypophysial portal blood was examined in anesthetized rats. Hypophysial portal blood was withdrawn at a rate of 5.0 microliter/min into a chilled tube through a cannula placed over the stump of the pituitary stalk and segmented every 20 min by air bubbles. Immunoreactive somatostatin (IRS) in the plasma was extracted with acetic acid and acetone and quantified by RIA. Basal levels (mean +/- SE) of plasma IRS in the hypophysial portal blood were 646 +/- 36 and 317 +/- 44 pg/ml in urethane- and pentobarbital-anesthetized rats, respectively. Under urethane anesthesia, injection of synthetic neurotensin into the lateral ventricle at various doses in the range of 0.016--2 microgram/rat caused a significant and dose-related increase of plasma IRS levels in the hypophysial portal blood, and this effect of neurotensin was significantly (P less than 0.05) suppressed by pretreatment with diphenhydramine (1 mg/100 g BW, iv), a histamine receptor blocker. Enhancement of IRS release by neurotensin was also observed in pentobarbital-anesthetized rats. Intraventricular injection of substance P (10 microgram/rat), beta-endorphin (1 and 5 microgram/rat), or [Met5]enkephalin had no effect on the level of somatostatin in the hypophysial portal blood of urethane-anesthetized rats. These results suggest a release of hypothalamic somatostatin into the hypophysial portal blood in response to intraventricular administration of neurotensin, probably by a histaminergic mechanism.
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PMID:Effect of intraventricular injection of neurotensin and other various bioactive peptides on plasma immunoreactive somatostatin levels in rat hypophysial portal blood. 616 24

Somatostatin (4 micrograms/min, cyclic form) was infused for 24 h on six occasions in four patients with carcinoid ileal tumor and multiple liver metastases. During infusion, spontaneous flushes and/or diarrhea were markedly reduced with a return to the pretreatment pattern on the next day. Urinary 5-hydroxyindole acetic acid excretion and plasma gastrin were not significantly changed, whereas plasma insulin presented the expected decrease and rebound. These results confirm that carcinoid symptoms are somatostatin-sensitive but do not provide evidence that serotonin or gastrin play a major role in inducing these symptoms.
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PMID:Effects of somatostatin infusion in four patients with malignant carcinoid syndrome. 618 12

Two distinct carboxy-terminus-directed anti-substance P (SP) sera (R-1C and R-6G) were used to characterize immunoreactive SP (I-SP) in acetic acid extracts of anterior pituitary (AP) and posterior pituitary (PP) glands of adult male rats. The tissue concentrations of I-SP measured by R-1C and R-6G were comparable. The contents of I-SP were 600-1150 pg/AP and 25-52 pg/PP. I-luteinizing hormone releasing hormone and I-somatostatin (I-SOM) were undetectable in AP extracts, but PP extracts contained the equivalents of 325-785 pg I-SOM/gland. Serial dilutions of AP and PP extracts produced displacement curves with both SP antisera that were parallel to the respective synthetic SP standard and hypothalamic extract displacement curves. Gel filtrations of AP and PP extracts on a Sephadex G-25 column produced I-SP peaks eluting in the same fractions as synthetic SP and hypothalamic I-SP. However, the AP I-SP profile also revealed a side peak migrating between the void volume and the major I-SP peak. Neither immunoreactive species in the AP extract were eliminated when eluted with 6.0 M guanidine HCl, a strong denaturing agent. In vitro incubation of paired anterior hemipituitaries for 30 min in the presence of a 56 mM K+ concentration resulted in a significant (p less than .0001), 25-fold increase in the release of I-SP into the incubation medium above the mean control value. Radiofrequency lesions placed in the median eminence-arcuate region of male rats caused a significant (p less than .001) reduction of I-SP in both the AP and PP. These reductions were inversely related to the plasma prolactin values. The elevation in plasma prolactin was taken as an index of completeness of lesions. We conclude that: 1) the rat pituitary contains I-SP as assessed by its immunologic and chromatographic behavior, 2) K+ depolarization is a potent stimulator of the release of AP I-SP in vitro, 3) the ME-arcuate region is important for the maintenance of pituitary I-SP levels in the rat.
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PMID:Partial characterization of immunoreactive substance P in the rat pituitary gland. 619 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

A fraction increasing water and sodium absorption in rat duodenum was detected in the material obtained at an early stage of purification of the hitherto isolated duodenal hormones. In Wistar rats, duodenal loops were made in situ and filled with a solution containing 0.138 mM NaCl, with 14C PEG and 22Na as markers; the final content was collected after 1 h and the movements of water and Na measured. In contrast to secretin, cholecystokinin, and somatostatin, which induced duodenal secretion, and with pentagastrin, which induced duodenal absorption and stimulated acid secretion, this fraction induced duodenal absorption f Na and water without stimulating acid secretion. The fraction was obtained by chromatography of a concentrate of intestinal peptides in 0.2 M acetic acid on Sephadex G25 (fine), and its active component was found to be methanol-soluble at pH4 and insoluble at pH7.5. It was eluted from carboxymethylcellulose 22 with 0.04 M ammonium bicarbonate and gel filtration of Sephadex G50 *fine), resulting in a tenfold increase in activity. Incubation with chymotrypsin suppressed the biological activity, indicating a peptidic nature. The substance displayed biological and radioimmunological properties distinct from those of the gastrointestinal hormones. Particularly, no cross-reactivity was found with gastrin, prolactin, and angiotensin, which are known to increase intestinal absorption. It therefore seems possible that the activity described is due to a peptide that has as yet not been isolated. The name 'sorbin' is proposed for this active principle.
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PMID:Sorbin, a peptide contained in porcine upper small intestine which induces the absorption of water and sodium in the rat duodenum. 679 42

The characteristics of terbium-161 diethylene triamine penta-acetic acid (DTPA) labelled octreotide with respect to specific binding to somatostatin (octreotide) receptors on rat brain cortex membranes, biological activity, uptake and excretion by isolated perfused rat livers and metabolism in vivo in normal and tumour-bearing rats were determined and compared to those of indium-111 DTPA-octreotide. The results of the binding studies demonstrate that 161Tb-DTPA-octreotide is a high-affinity radioligand for somatostatin receptors, with an affinity comparable to that of 111In-DTPA-octreotide. Rat growth hormone secretion inhibition experiments showed that 161Tb-DTPA-octreotide has a similar potency to 111In-DTPA-octreotide. 161Tb-DTPA-octreotide appeared to be taken up even less by the isolated perfused rat liver than 111In-DTPA-octreotide, as almost no tracer disappeared from the perfusion medium. Furthermore, hardly any radioactivity was found in the liver, and excretion into the bile was negligible. The biodistribution studies showed that for octreotide receptor-positive organs, such as pancreas and adrenals, uptake of 161Tb-DTPA-octreotide is lower then that of 111In-DTPA-octreotide. However, as the clearance from the blood of the former compound is faster than that of the latter, the tissue/blood ratio is higher in the case of 161Tb-DTPA-octreotide than with 111In-DTPA-octreotide. Furthermore, these studies demonstrated that the uptake of 161Tb-DTPA-octreotide by the renal tubular cells after glomerular filtration can be reduced by administration of lysine or sodium maleate. Increase in urine production before and during the experiment had no effect on the kidney uptake of 161Tb-DTPA-octreotide.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evaluation in vitro and in rats of 161Tb-DTPA-octreotide, a somatostatin analogue with potential for intraoperative scanning and radiotherapy. 749 21

Adolescent growth is regulated by developmental increases in growth hormone (GH) secretion. Although the hypothalamic release of GH-releasing hormone (GHRH) stimulates and the release of SRIF inhibits GH secretion, it is not known how these regulatory mechanisms change developmentally. In addition, GH secretion is facilitated during maturation by increases in peripheral estradiol and may be inhibited, via a negative feedback mechanism, by insulin-like growth factor-I (IGF-I). It is not clear whether these act through the hypothalamic regulation of GHRH and somatostatin (SRIF). In order to further understand the regulation of GH secretion during development, the present study determined how estradiol and IGF-I altered SRIF mRNA in the hypothalamus in immature female rats. The working hypotheses were that estradiol would decrease SRIF mRNA accounting, in part, for its positive effect on GH release and IGF-I would increase SRIF mRNA representing a negative feedback mechanism regulating GH secretion. Preprosomatostatin (ppSRIF) mRNA levels within the periventricular nucleus (PeVN) were measured with in situ hybridization in ovariectomized female rat pups (n = 5 per group). Infusions were delivered sc via either a Silastic capsule (oil, 10 or 60 micrograms/ml estradiol) or an osmotic minipump (acetic acid, 120 or 240 micrograms IGF-I/day). Following ovariectomy on Day 21, animals were treated for either 1 or 7 days beginning on Day 24 of age. A total of 18 treatment groups were evaluated, including control, estradiol alone, IGF-I alone, and estradiol and IGF-I combined at both doses and treatment durations.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Somatostatin mRNA levels within the periventricular nucleus are regulated by estradiol and insulin-like growth factor-I in immature female rats. 770 27

We have previously shown that the somatostatin (SRIH) precursor (pro-SRIH) and SRIH are present in the normal human pituitary, whereas mature SRIH is never detected in GH-secreting adenomas associated with high plasma GH levels, and pro-SRIH is absent in 50% of them. Considering the fact that GHRH is present and released in vitro in higher amounts from GH adenomas than from normal human pituitaries, the possibility of a negative control exerted by GHRH on pituitary SRIH was investigated. When GH-secreting adenomas were incubated for 4 h in the presence of GHRH (10(-8) mol/L), the amount of pro-SRIH, quantified after Sephadex G-50 filtration of the acetic acid extracts, was significantly decreased. The percent inhibition was negatively correlated to the amount of endogenously released GHRH measured in the control incubation medium, suggesting a local negative feedback control exerted by pituitary GHRH on pituitary SRIH. This was further demonstrated when adenomas were incubated with a GHRH antibody. Indeed, the presence of the GHRH antibody resulted in a significant increase in the content of pro-SRIH in the adenoma. Similar results were obtained for in vitro SRIH release; exogenous GHRH induced an inhibition of SRIH release from GH-secreting adenomas, and the GHRH antibody had the opposite effect. Using a perifusion system, we showed the concomitance between the increase in GH release and the decrease in SRIH release after GHRH stimulation. Together, these results show in vitro a negative control exerted by GHRH (both exogenous and locally released) on adenomatous pituitary SRIH. This further amplifies the importance of autocrine or paracrine controls in these tumors.
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PMID:Growth hormone (GH)-releasing hormone tonically inhibits in vitro endogenous somatostatin in human GH-secreting tumors. 774 20

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