Enhanced intestinal insulinotropic effect in streptozotocin-diabetic rats

To study the intestinal insulinotropic effects in the diabetic state, an investigation was made into the release of insulin from isolated rat pancreas perfused with portal venous effluent (PVE) obtained from the isolated perfused intestine of streptozotocin-induced diabetic rats. Rat intestine was perfused with Krebs-Ringer bicarbonate medium for 1 h, and the PVE was collected from both untreated and glucose-treated intestines of control and diabetic rats. The PVE, after adjusting its glucose concentration to the desired level, was used as the perfusing medium for the pancreas of a different rat. Glucose concentration in the perfusion medium was maintained at 5.5 mM for 20 min and at 16.7 mM for the next 30 min. Insulin output from pancreas perfused with PVE from untreated intestine of diabetic rats (252 +/- 45 ng/30 min, mean +/- SD) was similar to that of controls (269 +/- 72 ng/30 min). Pancreatic insulin output with PVE from glucose-treated intestine of diabetic rats (579 +/- 100 ng/30 min) was significantly greater compared with either that using PVE from untreated intestine of diabetic rats (P less than 0.01) or that from glucose-treated intestine of control rats (368 +/- 57 ng/30 min) (P less than 0.02). These results indicate that the insulinotropic effect is markedly enhanced in streptozotocin-induced diabetic rats.