Release of pancreatic and gastric somatostatin-like immunoreactivity in response to the octapeptide of cholecystokinin, secretin gastric inhibitory polypeptide, and gastrin-17 in dogs

The effects of the gastrointestinal hormones cholecystokinin- octapeptide (CCK-OP), secretin, gastric inhibitory polypeptide (GIP), and gastrin-17-I, infused at approximately their physiological rate, upon the release of pancreatic and gastric somatostatin-like immunoreactivity (SLI) were studied in dogs. In anesthetized dogs, CCK-OP, administered iv at a rate of 0.5 μg/kg·h, elicited increases in plasma levels of SLI of approximately 60 pg/ml in the inferior vena cava, 300 pg/ml in the pancreatic vein, 280 pg/ml in the fundic vein, and 300 pg/ml in the antral vein. During the infusion of secretin at a rate of 0.1 C.U./kg·h, inferior vena caval and gastric vein SLI levels did not change, although pancreatic vein SLI rose by 160 pg/ml with secretin administered at a supraphysiological rate of 1.0 C.U./kg·h, inferior vena caval SLI levels rose 30 pg/ml, pancreatic venous SLI levels rose 240 pg/ml, and fundic and antral venous SLI levels rose 120 and 160 pg/ml, respectively. GIP, infused at a rate of 1.0 μg/kg·h, did not affect fundic venous, antral venous, or inferior vena caval SLI levels, although pancreatic venous SLI levels rose 230 pg/ml. Gastrin 17-1, infused at a rate of 0.1 μg/kg·h, had no effect on SLI release. A mixture of the foregoing hormones was infused iv in conscious dogs in doubling doses, beginning with a minimum rate of 0.05 μ/kg·h CCK-OP, 0.05 C.U./kg·h secretin, 0.05 μg gastrin-17-I, and 0.4 μg/kg·h GIP. At the lowest infusion rate, peripheral venous levels of SLI rose by 35 pg/ml within 20 min. It is concluded that: 1) the canine pancreatic D cell is stimulated by low doses of CCK-OP, secretin, and GIP, but at such doses only CCK-OP stimulates gastric D cell function and augments SLI levels in the peripheral circulation; and 2) the peripheral venous SLI levels of conscious dogs rise in response to a physiological mixture of gastrin, CCK-OP, secretin, and GIP. Thus, these hormones may mediate, at least in part, the postprandial rise in SLI.