GASTRIC-INHIBITORY POLYPEPTIDE AND GLUCAGON-LIKE PEPTIDE-1(7-36) AMIDE EXERT SIMILAR EFFECTS ON SOMATOSTATIN SECRETION BUT OPPOSITE EFFECTSON GASTRIN-SECRETION FROM THE RAT STOMACH

Previous studies on the isolated perfused stomach have shown that gast ric inhibitory polypeptide (GIP) and glucagon-like peptide-1(7-36) ami de (GLP-1(7-36) amide) stimulate release of somatostatin (somatostatin -like immunoreactivity, SLI). GIP produced a paradoxical increase in g astrin secretion, whereas GLP-1(7-36) was inhibitory. In the current s tudy, the actions of synthetic (sp) and native (np) porcine and synthe tic human (sh) GIP, GLP-1(7-36), and GLP-1(7-37) on SLI and gastrin se cretion were compared using a gradient perfusion of peptide. All pepti des increased SLI secretion at a threshold concentration of similar to 50 pmol/L (p < 0.05). The initial rate of increase in response to spG IP (119 +/- 39 pg/min) was greater than with other forms of GIP or GLP -1. Maximal increases obtained with the two porcine peptides did not d iffer. Gastrin secretion was increased by concentrations of spGIP and npGIP similar to those increasing SLI secretion, but the maximal respo nse to shGIP was lower. In contrast to GIP-induced increases, both GLP -1(7-36) and GLP-1(7-37) suppressed gastrin secretion. It is concluded that human and porcine GIP, GLP-1(7-36), and GLP-1(7-37) all stimulat e SLI secretion but with different maximal effects, and GIP stimulates gastrin secretion whereas both forms of GLP-1 inhibit gastrin secreti on.