Role of calcium in defective insulin secretion from human and transplantable rat islet cell tumours

Abstract

Regulation of B-cell function was examined using pieces of a benign islet cell tumour from a 60-year-old woman, and isolated cells from a serially transplantable rat insulinoma. Acute incubations were performed after 3-days culture in RPMI-1640 containing 11.1 mM glucose. A variety of nutrients and drugs with established effects on pancreatic B-cell function failed to affect 45Ca uptake or insulin release by human tumour pieces. These included glucose alone or in combination with theophylline, glyceraldehyde, mannoheptulose, diazoxide, KCl, verapamil, D-600 and trifluoroperazine. The ineffectiveness of diazoxide was confirmed in long term cultures. Freshly isolated or 3-day cultured rat insulinoma cells also failed to respond to glucose with increased 45Ca uptake and insulin release. The results indicate an important role of calcium in the defective stimulus-secretion coupling of insulin-producing islet cell tumours.