Effect of Angiotensin II on Immunoreactive Insulin

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Abstract
Epinephrine and norepinephrine infusions, in man, inhibit immunoreactive insulin (IRI) responses to intravenous (iv) glucose, tolbutamide and glucagon. To determine the specificity of the reaction to catecholamine infusion, the effect of a non-adrenergic vasoconstrictor, angiotensin II, on the IRI response to glucose and tolbutamide was studied. Normal volunteers served as their own controls and either oral or iv glucose or tolbutamide was administered, with and without a continuous infusion of angiotensin II. A marked inhibition of IRI response to oral and iv glucose and to tolbutamide occurred during the infusion of angiotensin II. Following the infusion, a significant rise in IRI ensued. The comcomitant administration of phentolamine and angiotensin II did not modify the inhibition of IRI response. IRI response to oral glucose during angiotensin II was significantly greater than to iv glucose. The similar inhibitory effects of catecholamines and angiotensin II on IRI responses suggest that changes in pancreatic perfusion may influence insulin secretion. The greater IRI responses to oral than to iv glucose may depend in part upon changes in splanchnic circulation.