Stimulatory effect of neurotensin on insulin and gastrin secretion in dogs.

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The effects of synthetic neurotensin on plasma insulin and gastrin secretion were investigated in twelve normal and eight hypophysectomized (10th to 14th day post hypophysectomy) dogs. Neurotensin was injected rapidly or infused for 30 min into the superior pancreaticoduodenal artery, and plasma insulin and gastrin were measured by radioimmunoassay.In normal dogs, rapid administration of neurotensin (10μg/kg body wt) brought about a mild hyperglycemia and a rapid and sharp increase of plasma insulin and gastrin levels. In the pancreatic vein, a biphasic insulin response was noted. The same secretory pattern of insulin was demonstrated during neurotensin (500ng/kg/min) infusion. In the antral vein, the plasma gastrin level increased rapidly to 425% from basal level within 2 min and returned nearly to the initial level within 10 min after a rapid administration of neurotensin.In hypophysectomized dogs, the basal levels of plasma glucose, pancreatic insulin and antral gastrin were decreased to 53%, 9%, and 65% of normal dogs, respectively. Neurotensin has a little effect on insulin secretion, and a biphasic insulin secretory pattern observed in normal dogs was not demonstrated in hypophysectomized dogs. It seems likely that hypophysis may in part play a role in the neurotensin-induced insulin secretion. However, neurotensin-stimulated plasma gastrin concentrations were considerably maintained. Also, xenopsin (10μg/kg body wt) induced a mild hyperglycemia, hyperinsulinemia and hypergastrinemia, but its secretory activities were smaller than those of neurotensin.Neurotensin appears to stimulate the insulin and gastrin secretion by the mode action of neurogenic vasodilatation or by the direct action of pancreatic beta cell and gastrin secretory cell of the gastric antrum. Neurotensin may play an important role in the entero-insular axis.