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Introduction Somatostatin (or somatotropin release-inhibiting factor, SRIF) acts through five specific G-protein-coupled membrane receptors (SSTRs), code named sstr 1–5 , expressed in SRIF-target cells ( Patel 1999 , Møller et al . 2003 ). SRIF
Endocrinology Unit, Department of Internal Medicine and Medical Specialties, School of Medical and Pharmaceutical Sciences, University of Genova, Genova, Italy
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Endocrinology Unit, IRCCS Ospedale Policlinico San Martino, Genova, Italy
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Introduction Somatostatin receptors (SSTs) belong to the family of seven transmembrane G protein-coupled receptors (GPCRs) ( Günther et al. 2018 ). Five different SST subtypes have been identified, named SST 1 to SST 5 ( Günther et al
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ABSTRACT
The influence of somatostatin on thyroid function has been examined in immature domestic fowl passively immunized with somatostatin antiserum. Plasma thyroxine (T4) and tri-iodothyronine (T3) concentrations were markedly increased within 10 min of antisomatostatin administration and remained raised for at least 5 h. The increases in the T3 and T4 concentrations following somatostatin immunoneutralization were directly related to the volume of antisera administered. The increase in the T3 concentration exceeded the increase in the T4 concentration, resulting in a T3: T4 ratio greater than unity. While the raised T4 concentration began to decline 30 min after antisomatostatin administration, raised T3 concentrations were sustained for at least 2 h, and further increased the plasma T3: T4 ratio.
These results demonstrate that somatostatin immunoneutralization stimulates thyroid function in fowl. The magnitude and rapidity of the thyroidal responses to somatostatin immunoneutralization suggests that they occur independently of the hypothalamic-pituitary-thyroid axis. Somatostatin appears to exert a tonic inhibitory control on avian thyroid function, possibly by effects mediated at the thyroid gland to inhibit T4 release and by peripheral effects to suppress the conversion of T4 and T3.
J. Endocr. (1986) 110, 127–132
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-Arancibia et al. 2004 ). BDNF has thus been shown to increase mRNA and peptide levels of neuropeptide Y and somatostatin (SRIH) in cultured cortical ( Nawa et al. 1993 ) and striatal ( Mizuno et al. 1994 ) neurons. In BDNF-knockout mice, the density of
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on prolactin and GH secretion in pituitary cells dispersed in vitro , in combination with well-established secretagogues such as angiotensin II (Ang II), dopamine, growth hormone-releasing hormone (GHRH) and somatostatin. Furthermore, we investigated
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Introduction Octreotide is a potent somatostatin analog most commonly used to reduce blood levels of GH and insulin-like growth factor-1 (IGF1), also known as somatomedin C, in acromegaly patients ( Lamberts et al . 1993 , Yang & Keating 2010
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kisspeptin-13 on insulin, glucagon, and somatostatin secretion. The study was performed in the isolated perfused rat pancreas. Animals, materials, and methods Animals Male Wistar rats (200–225 g body weight) from our inbred colony were used as
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ABSTRACT
A sensitive and specific radioimmunoassay without an extraction step was developed for somatostatin in duck plasma. Degradation of Tyr1-125I-labelled somatostatin-14 (S-14) averaged 2% for blood collected with EDTA and zymofren. Recovery of somatostatin-like immunoreactivity (SLI), added to the plasma, averaged 91% for S-14 and 86% for S-28. Chromatographic analysis of portal plasma on Sephadex G-25 showed three peaks: one peak coeluted with cytochrome c (mol. wt 12 500) in the void volume and was called 'big' somatostatin; of the two smaller forms, one coeluted with synthetic S-28 and the other with synthetic S-14; these were immunologically and physicochemically indistinguishable from synthetic S-28 and S-14. In peripheral plasma only the large form of somatostatin, 'big' somatostatin, was found. The mean portal plasma concentration of SLI was 4·1 ±0·41 μg/l (n = 11, range 2·8–5·1 μg/l). In peripheral plasma the SLI concentration was 1·05 ±0·45 μg/l (n = 11, range 0·84–1·2 μg/l). The metabolic clearance rate, distribution volume and calculated half-life values were 63·1 ± 14 ml/kg per min, 40·9±8·9 ml/kg and 1·06±0·19 min for S-14 compared with 45·7 ±7 ml/kg per min, 14·8 ±2·5 ml/kg and 2·14± 0·54 min for S-28. These results indicated that S-28 was cleared from plasma at a slower rate than S-14 in the duck. It was concluded that: (1) portal plasma SLI was four times higher than peripheral SLI; (2) SLI in portal plasma existed as 'big' somatostatin, S-28 and S-14, whereas in peripheral plasma it existed mainly as 'big' somatostatin; (3) invivo studies indicated that S-28 was metabolized less rapidly than S-14.
J. Endocr. (1984) 100, 329–335
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The products of somatostatin in the circulation have been investigated by high-pressure liquid chromatography. Plasma collected 1 min after intravenous injection of cyclic (oxidized) somatostatin showed a single ultraviolet absorbing peak. The total plasma content of this product was equivalent to 10–20% of the injected dose. Amino acid analysis showed that 80–90% of the material in the peak was [des-Ala1]-somatostatin and the remainder was unchanged peptide. [des-Ala1]-Somatostatin is rapidly formed in blood and plasma in vitro and according to other workers may be fully active. In contrast, 1 min after injection of linear (reduced) somatostatin, no products could be detected in the circulation. Incubations in vitro resulted in rapid conversion of the linear somatostatin to a product similar to the cyclic form. However, in vivo, very efficient clearance of linear somatostatin must occur even more rapidly than cyclization. In view of the very different clearance rates of the two forms of somatostatin, it is important to know whether endogenous somatostatin is released in the cyclic or the linear form. The absence of detectable concentrations of inactive peptide fragments in the circulation suggests that inactivation of somatostatin occurs in the tissues.
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ABSTRACT
A continuous line of somatostatin-producing medullary thyroid carcinoma cells was established from a transplantable tumour in BALB/c mice. Virtually all of the somatostatin immunoreactivity co-chromatographed with somatostatin 14. The tumour cells replicated in spinner cultures with a doubling time of approximately 4 days, and the concentration of somatostatin released into the culture medium increased in proportion to the number of cells. Two-to threefold increases in amounts of stored and released somatostatin were observed after treatment of the cells with bromodeoxyuridine. This cell line might be valuable for studies of somatostatin regulation in normal and neoplastic C-cells, and for other studies of C-cell biology which require a mouse model.
J. Endocr. (1986) 110, 309–313
