Ventral and dorsal areas of rat pancreas: islet hormone content and secretion.

Islets isolated from the dorsal and ventral areas of the rat pancreas (dorsal and ventral islets) were found to have similar insulin and total protein contents. Dorsal islets, however, contained more glucagon and somatostatin than ventral islets. Dorsal islets secreted significantly more insulin in the presence of 16.7 mM glucose and 20 mM D-glyceraldehyde than did ventral islets. Leucine-induced (20 mM) insulin secretion from the two types of islet was similar. The amounts of somatostatin secreted by the two types of islet were similar both in the presence of 16.7 mM glucose and in the presence of 20 mM D-glyceraldehyde. By contrast, more glucagon was secreted by dorsal than by ventral islets in the presence of 16.7 mM glucose. It was found that the difference in glucagon secretion between the dorsal and ventral islets in the presence of 16.7 mM glucose may be an explanation for the difference in the rate of insulin secretion under these conditions. The results suggest that glucagon may exert an important intraislet control on insulin secretion.