The role of gastrointestinal peptides on pancreatic secretion in response to different stimulants in conscious rats.

Effects of intragastric food, intraduodenal amino acids, and intravenously administered bombesin and gastrin-releasing peptide (GRP) were examined in conscious rats with pancreatic fistula in terms of responses of exocrine pancreatic secretion, plasma levels gastrin, and cholecystokinin (CCK). Pancreatic juice and blood samples were collected at regular intervals before and after the stimuli. Intragastric food increased pancreatic secretion and plasma levels of gastrin and CCK. Intraduodenal infusion of amino acids had no effect on pancreatic secretion and plasma levels of gastrin and CCK. Intravenous infusion of bombesin at 1 microgram/kg/h induced significant increases in pancreatic volume and protein outputs, but had no effect on plasma levels of gastrin and CCK. Bombesin infusion at 10 micrograms/kg/h resulted in significant increases in pancreatic volume and protein outputs as well as plasma gastrin levels, but had no effect on plasma CCK levels. Intravenous infusion of GRP induced increases in pancreatic volume and protein outputs and plasma gastrin levels, but had no effect on CCK levels. Antrectomy resulted in significant decreases in basal levels of plasma gastrin. GRP-stimulated pancreatic volume and protein outputs were not significantly changed by antrectomy. In rats that underwent antrectomy, GRP infusion significantly increased pancreatic volume and protein outputs, but had no effect on plasma levels of gastrin and CCK. Food-stimulated pancreatic secretion and plasma levels of gastrointestinal peptides of rats were similar to other species, but amino acids, bombesin, or GRP may not be the stimulants for CCK release in rats. The stimuli that release CCK from duodenal mucosa probably varies among species.