Various sequential combinations of 20 gm. of glucose and 20 gm. of arginine were given as separate, twenty-minute infusions with a thirty-minute rest interval between infusions, to six nonobese, nondiabetic subjects. The sequence of glucose preceding arginine significantly enhanced the serum immunoreactive insulin response to this amino acid. Other sequences of glucose and arginine did not result in enhancement. The effect of a separate infusion of glucose preceding arginine was quantitatively similar to enhancement of insulin secretion by glucose (20 gm.) and arginine (20 gm.) infused simultaneously over twenty minutes. The response to arginine after glucose, however, resulted in earlier peak insulin levels than did the simultaneous glucose-arginine infusion.
These results imply a difference in the insulin-releasing mechanisms of arginine and glucose. It is suggested that certain time-dependent reactions, as well as a prior elevation of blood glucose are required for the enhancing influence of glucose on arginine-induced insulin secretion.