Effect of amino-acids on secretion of insulin by isolated islets of the monkey.

Insulin secretion was monitored in monkey islets isolated by collagenase digestion and exposed to leucine and arginine with and without glucose. Leucine by itself (10 to 40 mmol/l) elicited concentration-dependent insulin secretion. At 40 mmol/l, leucine was approximately 60% as effective as glucose (16.7 mmol/l). The response to leucine was increased at low glucose concentrations. In high concentrations (20 and 40 mmol/l), arginine by itself was a poor stimulant. The effect of arginine was enhanced at low glucose concentrations (2.8 to 5.6 mmol/l). At high glucose concentrations neither amino-acid produced any significant further increase in insulin release.