Colocalization of calcitonin gene-related peptide and somatostatin in pancreatic islet cells and inhibition of insulin secretion by calcitonin gene-related peptide in the rat.
Calcitonin gene-related peptide (CGRP)- and somatostatin (SRIF)-containing cells were identified by immunocytochemical techniques in pancreatic islet cells of the rat. CGRP-containing cells were found primarily in the peripheral portion of the pancreatic islets. In addition, CGRP-containing cells also contained somatostatin, which identifies the islet CGRP-containing cells as D cells. In the present study, we also tested the effect of CGRP on gastrin-releasing peptide (GRP; 10(-9) M)- or cholecystokinin (CCK-8, 10(-9) M)-stimulated release of insulin from isolated rat islets in vitro. At concentrations of 10(-8)-10(-11) M, CGRP inhibited GRP- and CCK-8-stimulated release of insulin significantly when compared with GRP or CCK-8 alone. At the lowest concentration of CGRP (10(-11) M), the inhibitory effect of CGRP on CCK-8-stimulated release of insulin was statistically significant (p less than 0.05) and exceptionally potent (65-90% inhibition). We have also found that CGRP does not stimulate the release of SRIF from isolated islet cells. These findings suggest that CGRP may play a regulatory role in the release of insulin.
D000818:Animals; D015740:Calcitonin Gene-Related Peptide; D002766:Cholecystokinin / Q000494:pharmacology; D019886:Gastrin-Releasing Peptide; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000032:analysis*; D008297:Male; D009479:Neuropeptides / Q000032:analysis* / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000032:analysis*; D014665:Vasodilator Agents
D007328:Insulin; D009479:Neuropeptides; D010455:Peptides; D014665:Vasodilator Agents; D013004:Somatostatin; D019886:Gastrin-Releasing Peptide; D002766:Cholecystokinin; D015740:Calcitonin Gene-Related Peptide