Role of Calcium in Glucagon Secretion

The role of calcium ions in the process by which nutrients affect glucagon secretion by pancreatic islet α-cells remains the matter of an apparently endless debate. In the prolongation of recent articles dealing with this matter, the present review draws attention to the dual role of Ca2+ as revealed by prior publications. In such a perspective, emphasis is placed on the increase in glucagon output in response to the omission of extracellular Ca2+ as recorded in the presence of D-glucose or 2-ketoisocaproate, the permissive role of extracellular Ca2+ in the positive secretory response to arginine or a mixture of fumarate, glutamate and pyruvate, and the effects of an organic calcium-antagonist on glucagon output. Considering the role currently ascribed to Ca2+ in the activation of motile events involved in stimulus-secretion coupling, attention is also given to the effects of cytochalasin B, D2O and mitotic-spindle inhibitors upon the secretory response of α-cells exposed to D-glucose in the absence or presence of arginine.