Insulinotropic action of amino acids at their physiological concentrations: I. Experiments in incubated islets

In order to simulate physiological conditions, the influence of a mixture of 22 amino acids together with taurine, all tested at their normal concentration in plasma, upon insulin release, D-glucose metabolism and 45Ca net uptake was investigated in isolated rat pancreatic islets. The amino acid mixture had little effect upon insulin release at low concentrations of D-glucose but augmented, by up to 50%, the release of insulin provoked by higher concentrations of D-glucose. The effects of glibenclamide, forskolin, theophylline and cytochalasin B upon insulin release evoked by D-glucose in the absence or presence of the amino acid mixture and the changes in insulin output evoked by the omission from the amino mixture or addition to media containing only D-glucose of selected amino acid(s), as well as the influence of the amino acid mixture upon D-glucose metabolism and 45Ca net uptake, were considered as compatible with both the role of certain amino acids as nutrients and the accumulation of other amino acids as positively charged molecules in the islet cells.