Effect of somatostatin-28 on dynamics of insulin secretion in perfused rat pancreas.
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 beta-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.
Ensinck
J W
JW
Department of Medicine, University of Washington, Seattle 98195.
Laschansky
E C
EC
Vogel
R E
RE
D'Alessio
D A
DA
D000328:Adult; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005215:Fasting; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D010477:Perfusion; D011498:Protein Precursors / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013004:Somatostatin / Q000494:pharmacology*; D053561:Somatostatin-28; D013997:Time Factors
D007328:Insulin; D011498:Protein Precursors; D013004:Somatostatin; D053561:Somatostatin-28