Is somatostatin a true local inhibitory regulator of insulin secretion?

Pancreatic somatostatin was depleted after oral administration of cysteamine to rats, yet the B-cells in the isolated islets were morphologically and functionally intact. Compared with islets from the rats not given cysteamine, the somatostatin-depleted islets released larger amounts of insulin during 1 h of incubation by glucose or 3-isobutyl-1-methylxanthine stimulation. Therefore, the possibility that pancreatic somatostatin may locally regulate the inhibitory effects of insulin secretion has to be considered.