An osmotic-sensitive taurine pool is localized in rat pancreatic islet cells containing glucagon and somatostatin

Previous reports have dealt with the hypoglycemic properties of taurine and its effects on insulin secretion by adult and fetal isolated islets. We ha ve studied the presence and cellular distribution of taurine in rat islets, the conditions to evoke its release, and its possible modulatory action on insulin secretion. We localized taurine by techniques of double immunolabe ling in most glucagon-positive cells and in some somatostatin-positive cell s, whereas insulin-positive cells were not labeled with the taurine antibod y. Although high-glucose stimulation did not evoke any taurine release, a h yposmotic solution (17% osmolarity reduction) induced a specific phasic rel ease of taurine and GABA (34 and 52% increase on their basal release rate). On the other hand, taurine (10 mmol/l) application slightly reduced the se cond phase of insulin secretion induced by glucose stimulation. In conclusi on, taurine is highly concentrated in glucagon-containing cells of the isle t periphery. It is not liberated by glucose stimulation but is strongly rel eased under hyposmotic conditions. All of these data suggest that taurine p lays an osmoregulatory role in alpha -cells.