Suppressive effect of intragastric nutrients infusion on insulin release from perfused rat pancreas

Using the isolated and perfused rat pancreas preparations, we examined whether or not the direct transmission of signals from the gastro-duodenum to the pancreatic islets is existent. Pancreases were isolated en bloc with stomach and the proximal portion of duodenum and were perfused without recirculation. After perfusion with 5.5mM glucose in the perfusate for 40 minutes, 1 ml solution of the following nutrients (0.9% and 9% NaCl, 5% and 50% glucose, 5% and 50% fructose) was respectively infused into the stomach. And ten minutes after the infusion, the pancreas was perfused with 16.7 mM glucose for 20 minutes. Although the glucose-induced insulin release was similar to controls in the pancreas with intragastric infusion of 0.9% NaCl, 5% glucose, and 5% fructose, it was significantly lowered in the pancreas with intragastric infusion of 9% NaCl, 50% glucose, and 50% fructose. These results indicate that there is a direct transmission of some signals from the gastro-duodenum to the pancreatic islets through intragastric high osmolarity.