A Difference in Mechanism by Which Leucine and Other Amino Acids Induce Insulin Release1

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Abstract
Leucine, arginine, valine and a solution of 8 amino acids not containing leucine were administered intravenously to healthy subjects before and after administration of chlorpropamide. Leucine and arginine were administered to 9 patients with functioning pancreatic islet cell tumors. Infusions of arginine were given to healthy subjects before and after the intravenous administration of diazoxide. Leucine induced excessive release of insulin in all healthy subjects pretreated with chlorpropamide and in some of the patients with functioning islet cell tumors. On the other hand, insulin release was normal or reduced when these 2 groups of subjects received the other essential amino acids employed. Insulin release induced by the administration of arginine to healthy subjects was not suppressed by prior infusion of diazoxide. The results of these studies suggest that the mechanism by which leucine induces insulin release differs from the mechanism by which other essential amino acids induce release of insulin.