Requirement for calcium ion in insulin secretion by the perfused rat pancreas.

CURRY, DONALD L., LESLIE L. BENNETT, AND GEROLD M. GR~DSKY. Requirement for calcium ion in insulin secretiorz by the perfused rut p ancreas. Am. J. Physiol. 214(l): 174-178. 1968.The effect of calcium ion on insulin release was studied in the isolated perfused rat pancreas. Following a standard glucose stimulus, insulin secretion (determined by immunochemical assay of the total portal vein effluent) was directly dependent on perfusate calcium ion concentrations up to 4 mEq/liter, At calcium levels greater than this, the total insulin release exhibited a plateau which was independent of calcium ion concentration. Following a standard 2-min tolbutamide stimulus, insulin release was directly dependent on the perfusate calcium concentration throughout the whole spectrum of calcium COP centrations studied (0.59-10.9 mEq/liter). At high calcium levels, insulin secretion was prolonged throughout a 6-min period of tolbutamide stimulation. Preparations which were perfused with solutions containing glucose, but to which no calcium had been added, failed to have a significant release of insulin. When calcium was added to the perfusates of these preparations, a marked increase in insulin secretion was observed (provided that the calcium deprivation lasted no longer than 20 min). Calcium ion itself will not produce a release of insulin, but it is necessary for normal insulin secretion in response to glucose or tolbutamide.