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 8-N-N-diethylamino octyl 3,4,5-trimethoxybenzoate (TMB-8) and trifluoperazine (TFP) on the early phase (10 min) of the release of pancreatic hormones from isolated rat islets were investigated. TMB-8 and TFP stimulated insulin, glucagon, and somatostatin release in a dose-dependent manner at a low glucose concentration (2.5 mM). The levels of glucagon and somatostatin release were also stimulated by these two agents at a high glucose concentration (10 mM). Their effects were independent of external calcium ion level. These two agents did not modify insulin release at the high glucose concentration. The stimulative effects of the two agents on the release of these hormones were partially suppressed when the islets were pretreated with 6-hydroxydopamine (6-OHDA), a chemical adrenergic denervator that acts at nerve endings. In this situation, the norepinephrine (NE) released from pancreatic islets decreased to 44% of that of non-treated islets (P less than 0.01). The addition of NE (10(-9) M) to the incubation medium increased insulin, glucagon, and somatostatin secretion by 20-30% over control levels (P less than 0.05). In conclusion, the early phase of pancreatic hormone release was stimulated by TMB-8 and TFP. Our results strongly suggest that these two drugs could be mediated by the NE released from nerve endings in the islets.
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PMID:Stimulative effects of TMB-8 and trifluoperazine on pancreatic hormone release. 256 59

The solubilization of somatostatin receptors from guinea-pig pancreas by different non-denaturing detergents was investigated after stabilization of the receptors by prior binding of 125I-[Tyr11]somatostatin or its analogue 125I-[Leu8,DTrp22,Tyr25]somatostatin 28, to pancreatic plasma membranes. The somatostatin-receptor complexes were solubilized in a high yield by Zwittergent 3-14 (3-[tetradecyldimethylammonio]-1-propanesulfonate), a zwitterionic detergent. Other detergents, digitonin, Triton X-100, Chaps (3-[cholamidopropyldimethylammonio]-1-propanesulfonate) and octyl beta-D-glycopyranoside, achieved only partial solubilization. The recovery of receptor complexes was increased by glycerol. In order to characterize solubilized somatostatin-receptor complexes, membranes receptors were covalently labelled using N-5-azido-2-nitrobenzoyloxysuccinimide as cross-linking reagent before solubilization. Gel filtration chromatography analysis resulted in the identification of a major protein component of apparent Mr = 93,000 which interacted with the two radioligands. In addition, a similar component of Mr = 88,000 was characterized after analysis by SDS-PAGE of membrane receptors covalently cross-linked with 125I-[Leu8,DTrp22,Tyr25]somatostatin 28 by different heterobifunctional reagents: N-5-azido-2-nitrobenzoyloxysuccinimide, N-hydroxysuccinimidyl 4-azidobenzoate, N-succinimidyl 6-(4'-azido-2'-nitrophenylamino)hexanoate. Optimal cross-linking results were obtained with N-5-azido-2-nitrobenzoyloxysuccinimide. The solubilized somatostatin-receptor complex was adsorbed to wheat-germ agglutinin-agarose column and eluted by specific sugars. We concluded that the guinea-pig pancreatic somatostatin receptor in the membrane and in the non-denaturing detergent solution behaves as a protein monomer of apparent Mr approximately 85,000-90,000. The somatostatin receptor is a glycoprotein which contains complex-type carbohydrate chains.
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PMID:Solubilization and characterization of guinea-pig pancreatic somatostatin receptors. 303 26

Somatostatin receptors from rabbit retinal membranes were solubilized in an active form using a mixture of the detergent n-octyl b-D-glucopyranoside (OG) and CHAPS. The binding of [125I]-Try11-somatostatin to the soluble extract was saturable and of high affinity, with an apparent affinity constant (Kd) of 0.60 +/- 0.20 nM and a maximum number of binding sites (Bmax) of 80 +/- 48 fmol/mg protein. The specific binding of [125I]Tyr11-somatostatin was inhibited in a dose-dependent manner only by the somatostatinergic analogs. The biochemical characteristics of both the membrane-bound and soluble receptors were studied by photoaffinity labeling techniques. Analysis by SDS-PAGE and subsequent autoradiography revealed the presence of a major protein of similar relative molecular mass (M(r) 54,000 and 57,000 for membrane and soluble sites, respectively). The photolabeling of this protein was specifically inhibited by somatostatin-28, somatostatin-14, SMS 201-995 (a synthetic octapeptide analog of somatostatin) but not by bombesin and somatostatin-28(1-14). The non-hydrolysable GTP analog guanosine-5'-O-(3-thio-triphosphate) (GTP gamma S) regulated the photolabeling of [125I]Tyr11-somatostatin to the membrane and soluble receptors. These studies describe for the first time the successful solubilization of the somatostatin receptor and the biochemical characterization of both membrane-bound and soluble receptors from rabbit retina.
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PMID:Solubilization of active somatostatin receptors from rabbit retina. 849 40

In experimental models and in humans, somatostatin (SRIF) is able to contract certain vascular structures. The present experiments were designed to assess the capacity of SRIF to contract cultured rat aortic vascular smooth muscle cells (VSMC), and to analyze the possible mechanisms involved. Cells incubated with SRIF showed a significant reduction in planar cell surface area, in a time- and dose-dependent manner. This effect was partially blocked by preincubating the cells with a combination of calcium antagonists (10 microM verapamil, plus 10 microM 3,4,5-Trimethoxybenzoic acid 3-(diethylanino) octyl ester TMB)-8). SRIF was also able to stimulate myosin light-chain phosphorylation in VSMC. A small but significant increase of intracellular calcium concentration, and decreased levels of cAMP, without changes in cGMP, were detected in VSMC incubated with SRIF. A search for the known SRIF receptors present in these cells, by reverse transcription-polymerase chain reaction, only SRIF receptor-4 was found to be present. These results demonstrate the ability of SRIF to contract cultured rat VSMC. The contraction observed in these cells appears to be due to a mixed mechanism, that involves [Ca2+]i and cAMP as second messengers, and is likely mediated via SRIF receptor-4.
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PMID:Mechanisms involved in the somatostatin-induced contraction of vascular smooth muscle cells. 1050 70

Octreotide (OCT) was recently found to have high binding affinity to the positive tumor cells of somatostatin receptors (SSTRs). In this study, octreotide-Phe-polyethylene glycol-stearic acid was first successfully synthesized and used as a targeting molecule for N-octyl-O, N-carboxymethyl chitosan (OCC). Doxorubicin (DOX) was loaded into OCT-modified OCC micelles (DOX-OCC-OCT). The drug-loaded micelles obtained exhibited spherical shape, small particle sizes, and negative zeta potentials. The cytotoxicity of DOX-OCC-OCT micelles against MCF-7 cells (SSTRs expressing) was found to significantly increase with the increased amount of OCT modification, whereas no significant difference was observed against WI-38 cells (no SSTRs expressing). Results of flow cytometry, fluorescence microscopy, and confocal laser scanning microscopy confirmed that DOX-OCC-OCT micelles could remarkably increase the uptake of DOX in MCF-7 cells. All the results indicated that OCC-OCT micelles may be a promising intracellular targeting carrier for efficient delivery of antitumor drugs into tumor cells.
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PMID:Octreotide-modified N-octyl-O, N-carboxymethyl chitosan micelles as potential carriers for targeted antitumor drug delivery. 2208 25

A multifunctional mixed micelle was assembled for drug targeting delivery by combining two newly synthesized amphiphilic polymers, which were octreotide-polyethylene glycol-monostearate (OPMS) and N-octyl-N-succinyl-O-carboxymethyl chitosan (OSCC), respectively. The mixed micelle was designed to be characterized with long circulation, somatostatin receptors (SSTR)-mediated endocytosis and pH sensitivity. A series of assembling proportions of OPMS and OSCC was tested to reveal the effect of compositions on the functions. The particle size, zeta potential, drug loading and critical micelle concentration were examined. The dialysis test indicated a pH-triggering release behavior of the doxorubicin-loaded mixed micelle (DLMM), and faster release in acidic media (pH 4.0-6.0) in response to the protonation of carboxyl group. In addition, the PEG segments could efficiently protect the mixed micelle from plasma protein adsorption in vitro, and the DLMM composed of 20% OPMS and 80% OSCC provided the longest residence time after intravenous injection in rats in vivo. Due to SSTR mediated endocytosis, the significantly higher uptake of DLMM was observed in the tumor cells (SMMC-7721), compared with that in the normal cells (CHO) without SSTR expression. All the results suggested that the mixed micelle with multifunctional characteristics could be used as an effective approach for tumor treatment.
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PMID:Octreotide-modified and pH-triggering polymeric micelles loaded with doxorubicin for tumor targeting delivery. 2211 55