Studies on insulin secretion in vitro from isolated islets of the rat pancreas.

Intact islets were isolated from the normal rat pancreas by the sedimentation technique and maintained in vitro. The islets did not destroy exogenous insulin added in vitro. Glucose in low concentrations (30 mg/100 ml) did not stimulate insulin secretion above base line values observed in the absence of glucose. High concentrations of glucose and mannose stimulated insulin secretion and the stimulatory action of glucose was inhibited by the addition of mannoheptulose. Galactose and fructose did not stimulate insulin release above base line values. Glucagon stimulated insulin secretion and the effect was enhanced in the presence of theophylline. Tolbutamide did not stimulate insulin secretion from isolated rat islets. However, a stimulatory effect of this agent was observed using isolated rabbit islets. The studies indicate that islets isolated by the sedimentation technique can be utilized for in vitro investigations of the direct effect of certain agents on insulin secretion. (Endocrinology 83: 1155, 1968)