Abstract
Studies on the role of calcium in insulin secretion from a transplantable hamster insulinoma were performed utilizing dispersed cell suspensions. Insulin release was positively correlated with the extracellular calcium concentration. Potassium (40 mM) and ouabain (10-3M) induced an increased calcium uptake by cells and a concomitant increase in insulin release. Verapamil (10-5M) reduced calcium uptake and insulin release in a parallel manner indicating that the calcium uptake was related to the insulin release. Glucagon, which stimulates insulin release by an adenosine 3′,5′-monophosphate (cAMP)-mediated mechanism, had no effect on calcium uptake and insulin release induced by glucagon was unaffected by verapamil. Therefore, cyclic AMP mediated insulin release does not appear to be the consequence of stimulation of calcium uptake. Glucose, which was transported and phosphorylated by insulinoma cells, did not induce calcium uptake or insulin release. In normal islets glucose did both. The results suggest t...
Published Version
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