Effect of Digestion on Gastric and Pancreatic Secretion Regulated by Gastrointestinal Hormones

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It has been well known that pancreatic enzymes have a most important role in the intestinal digestion, and gastric and pancreatic secretion is regulated by digestive products. We investigated the regulation of gastric and pancreatic secretion in response to intestinal nutrients (protein and fat) mediated by gastrointestinal hormones in rats.1.Effect of intraduodenal fat (fat, lipase-digested fat, and fatty acid) on gastric acid secretion and gastrin release was studied. Although lipase-digested fat and fatty acid inhibited acid secretion and gastrin release, fat failed the inhibitory effect under diversion of pancreatic juice. It means that fat digestion by lipase is necessary for the inhibitory action of intraduodenal fat on gastric acid secretion.2.Pancreatic stimulatory effect of intraduodenal long-and medium-chain trigyceride (LCT and MCT) was studied. Pancreatic secretion and CCK release was stimulated by LCT under pancreatic juice existed in the duodenum, but not affected by MCT.Under pancreatic juice diversion, LCT failed to stimulate pancreatic secretion. Thus, LCT digestion by pancreatic juice is necessary for stimulating pancreatic secretion.3.Effect of intraduodenal protein (casein) and amino acids on pancreatic secretion and release of secretin and CCK was studied. Casein protein stimulated CCK release and enzyme secretion. On the other hand, amino acids stimulated secretin release and bicarbonate secretion. Thus, protein digestion affects hormone release and pancreatic secretion.4.Intraduodenal administration of amino acids as well as fat, inhibited gastric acid secretion and gastrin release. The inhibitory action of amino acids was mediated by endogenous secretin released by amino acids.