Effects of gut hormone on insulin and glucagon secretion

To examine the possible influences of gastrointestinal hormones upon the secretion of the hormones of islets of Langerhans, highly purified preparations of gastrin, secretin and pancreozymin were injected endoportally in anesthetized dogs. All three hormones were found to cause an immediate rise in the concentration of insulin in the pancreaticoduodenal vein. The effect of gastrin on insulin release was quantitatively trivial, while that of secretin was more substantial and of longer duration; however, pancreozymin appeared to be the most potent insulin stimulator and, in addition, caused a parallel rise in pancreatic glucagon secretion. Furthermore, pancreozymin was shown to augment both the insulin and the glucagon response to hyperaminoacidemia. Intraduodenal administration of amino acids, known to be the most potent stimulator of endogenous pancreozymin, was found to elicit a greater and more rapid release of insulin and glucagon than the intravenous administration of amino acids, suggesting that endogenous pancreozymin plays a physiologic role in augmenting the islet cell hormone response to ingested amino acids. The physiologic augmenter of the insular response to ingested glucose remains unidentified, however.