Possible role of the stomach in enteroinsular axis in rats

To elucidate the possible role of the stomach in enteroinsular axis, rats had both an inflow gastric cannula and an outflow diversion cannula and a duodenal inflow cannula. The effects of intragastric infusion of glucose (1 mL in 10% solution) or mannitol (1 mL in 10% solution) on blood and plasma insulin responses to subsequent intraduodenal glucose (1.5 g/kg in 10% solution) or amino acids (1.0 g/kg in 10% solution) infusion were investigated. Blood glucose and plasma insulin responses to intraduodenal amino acids were not altered by intragastric infusion of glucose or mannitol. However, higher blood glucose and lower plasma insulin responses to intraduodenal glucose were observed in the rat with intragastric infusion of glucose or mannitol compared with controls (intragastric infusion of distilled water). This phenomenon was abolished in the rat with preadministration of phentolamine. These results suggest that intragastric tonicity may suppress glucose-induced insulin secretion, probably through the alpha-adrenergic mechanism in the rat.