Plasma insulin concentration during physiological variations in immunoreactive plasma secretin.

The effect of endogenous and exogenous secretin on fasting plasma insulin and glucose concentrations in peripheral venous blood was studied. In 10 non-diabetic subjects intragastric instillation of 300 ml 0.1 mol/l hydrochloric acid increased the plasma secretin concentration significantly. This increment did not influence insulin or glucose concentration. Control experiments with intragastric instillation of 300 ml of isotonic saline did not influence the plasma concentration of secretin, insulin or glucose. In four other non-diabetic persons no significant changes were found in plasma insulin or glucose concentration during an i.v. infusion of pure natural porcine secretin in doses of 0.1, 0.3, 1.0 and 3.0 clinical units/kg/h. The results suggest that secretin is without effect on insulin secretion in the fasting normal subject.