Inhibition of Pancreatic Glucagon Responses to Arginine by Somatostatin in Normal Man and in Insulin-Dependent Diabetics

Abstract

Somatostatin, a recently synthesized hypothalamic peptide thought to represent growth hormone-release-inhibiting factor, has been previously shown to inhibit pancreatic glucagon secretion in species other than man. To determine whether somatostatin also inhibits human glucagon secretion, plasma glucagon responses during intravenous infusion of arginine alone (250 mg. per kilogram over twenty-five minutes) and in combination with synthetic cyclic somatostatin (20,μg. per minute) were compared in six normal and six insulin-dependent diabetic subjects. Somatostatin abolished glucagon responses to arginine in both groups, with plasma glucagon declining transiently below basal levels; this occurred despite the fact that the diabetic subjects had fasting hyperglucagonemia and exaggerated glucagon responses during control arginine infusions. In both groups plasma glucose rises seen after arginine were diminished during somatostatin infusions, and, in the normal subjects, insulin responses were also inhibited. These results demonstrate that somatostatin is a potent inhibitor of glucagon secretion in man. Accordingly, it may prove useful as an adjunct to insulin therapy in treatment of insulin-requiring diabetes mellitus.