Comparison of effects of neurotensin and fat on pancreatic stimulation in dogs.

In six conscious dogs with esophageal, gastric, and pancreatic fistulas, the effects of intravenous infusion of neurotensin and intraduodenal instillation of sodium oleate on gastric and pancreatic secretion were determined under basal conditions and after exogenous (secretin and cholecystokinin octapeptides) or endogenous stimulants (feeding and duodenal acidification). Neurotensin given intravenously in graded doses (1.5-200 pmol . kg-1 . min-1) to fasted dogs produced a dose-dependent stimulation of pancreatic bicarbonate and protein secretion reaching, respectively, about 18 and 100% of maximal responses to secretin and cholecystokinin octapeptide (CCK). Duodenal oleate in graded doses (0.5-16 mmol/h) resulted in a similar pattern of bicarbonate and protein secretion but increased plasma neurotensin only to about 10% of that achieved with infusion of exogenous neurotensin producing an equal rate of pancreatic secretion. Neurotensin, like oleate, potentiated the action of secretin and CCK on pancreatic bicarbonate and had additive effects on protein response to these secretagogues. Both neurotensin and oleate increased pancreatic response to liver extract meal kept in the stomach at constant pH (5.5) and the response to sham feeding but decreased the response to ordinary feeding, probably due to the inhibition of gastric acid secretion and reduction of duodenal acidification. Neurotensin given intra-arterially directly to the pancreas or to isolated intestinal segment increased dose dependently the blood flow and oxygen consumption without affecting general circulation. We conclude that 1) neurotensin mimics the pancreatic secretory effects of intestinal fat, 2) neurotensin may contribute in part to fat-induced stimulation of the pancreatic secretion, and 3) the secretory effects of neurotensin are accompanied by a marked stimulation of intestinal and pancreatic circulation and metabolism.