The effect of gastrin on basal and aminoacid‐stimulated insulin and glucagon secretion in man

Abstract. The effect of gastrin on basal and aminoacid‐stimulated glucagon and insulin secretion was studied in eleven normal young subjects. The concentrations of glucagon, insulin and gastrin in plasma or serum were measured radioimmunochemically. The results of amino‐acid‐stimulation were compared to those obtained during a protein‐rich meal. Intravenous injection of synthetic human gastrin‐17 in doses from 15.6 ng to 1 μg/kg increased the concentration of glucagon and insulin in peripheral venous blood to a maximum within 5 min. In spite of the enhanced concentrations of insulin induced by gastrin, corresponding concentrations of glucose were either unchanged or increased. Infusion of a mixture of fifteen aminoacids increased the concentrations of glucose, glucagon and insulin. While the increases in glucose and insulin concentrations were similar to those obtained after a protein‐rich meal, the glucagon response was much larger after the infusion. Injection of gastrin‐17 after 30 min of infusion of aminoacids did not potentiate either the glucagon or the insulin response. The results indicate that gastrin, besides stimulating insulin secretion, can also stimulate glucagon secretion in a dose‐dependent manner. The concentrations of gastrin necessary to stimulate glucagon secretion significantly correspond to the concentrations found in diseases with endogenous hypergastrinaemia (achlorhydria and Zollinger‐Ellison syndrome). While gastrin potentiates the glucose‐induced insulin secretion, it does not potentiate neither the aminoacid‐induced insulin nor glucagon secretion.