Somatostatin-28 (S-28), originating in gastrointestinal cells, is secreted into the circulatory system and rises in human plasma after ingestion of a mixed meal. Pancreatic β-cells contain specific, high-affinity receptors for S-28, and it is plausible that this peptide is a physiological modulator of insulin secretion. To evaluate the effects of physiological concentrations of S-28 on glucose-mediated insulin secretion, we used the perfused in situ rat pancreas under two conditions: 1) “square-wave” glucose infusion from 2.8 to 11.1 mM and 2) ramping of glucose at 0.28 mM/min throughout 45 min. S-28 concentrations of 16, 32, and 80 pM were separately coinfused for 40 min in the first condition and at 16 pM in the second condition. During square-wave glucose infusion, biphasic insulin secretion was elicited with marked attenuation of both phases during coinfusion with the two higher concentrations of S-28. At 16 pM S-28, which approximates postprandial At 16 pM S-28, which approximates postprandial concentrations, only first-phase secretion was suppressed. During ramping of glucose, insulin was released gradually and, in the presence of 16 pM S-28, was shifted to the right, indicating an increase in threshold glucose levels for insulin secretion. We concluded that S-28, at levels achieved postprandially, modulates the release of insulin by altering the threshold of sensitivity to glucose.
Effect of Somatostatin-28 on Dynamics of Insulin Secretion in Perfused Rat Pancreas
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John W Ensinck, Ellen C Laschansky, Robin E Vogel, David A D'Alessio; Effect of Somatostatin-28 on Dynamics of Insulin Secretion in Perfused Rat Pancreas. Diabetes 1 September 1991; 40 (9): 1163–1169. https://doi.org/10.2337/diab.40.9.1163
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