Enhanced insulin secretion and calcium uptake by Zucker "fatty" rat islets

The relationship of the net uptake of calcium to insulin secretion by pancreatic islets isolated from Zucker "fatty" rats and their lean counterparts was studied. Islets from "fatty" rats secreted 1.5 to 3 times as much insulin as did the lean rat islets over a glucose concentration range of 0 to 27.7 mM. Over the same glucose concentration range, calcium accumulation was 2-fold greater in islets from the "fatty" rats than from the others. Both insulin secretion and calcium uptake were 2 to 3 fold greater for islets from the "fatty" rats than those from the lean animals over an extracellular calcium concentration range of up to 5 mEq/L. The data indicate that for islets isolated from Zucker "fatty" rats insulin hypersecretion in response to glucose and extra-cellular calcium is associated with enhanced calcium accumulation.