Secretin is released by digestive products of fat in dogs

We investigated the effect of fat or digestive products of fat on the release of endogenous secretin in 15 gastric fistula dogs with either pancreatic fistulas or duodenal fistulas. In 4 dogs with both gastric and duodenal cannulas, intraduodenal administration of corn oil (Lipomul) at a dose of 15 mmol resulted in a significant increase in plasma secretin concentration, whereas in another group of 4 dogs with complete pancreatic duct ligation, the same amount of triglyceride failed to increase the secretin concentration. When Lipomul incubated with pancreatic enzymes was administered in the duodenum, a marked increase in plasma secretin concentration occurred in the 4 dogs with pancreatic duct ligations. In the 7 dogs with chronic pancreatic fistulas, intraduodenal administration of Lipomul resulted in a significant increase in both plasma secretin concentration and pancreatic secretion of bicarbonate when the pancreatic juice was allowed to flow into the duodenum, whereas no increase in either the secretin concentration or bicarbonate output was apparent using the same amount of Lipomul when the pancreatic juice was diverted from the duodenum. In 4 of these 7 dogs so studied, intraduodenal administration of oleic acid emulsion, with pH adjusted to 5.0 in graded doses, resulted in a dose-related increase in the secretin concentration that paralleled pancreatic bicarbonate output. The increases in both secretin concentration and pancreatic bicarbonate secretion were completely abolished by intravenous infusion of a rabbit antisecretin serum in the 4 dogs. Thus we conclude that release of endogenous secretin plays an important role in the mechanism of exocrine pancreatic secretion stimulated by digestive products of fat in dogs.