EFFECTS OF EXTRACELLULAR CALCIUM ON ELECTRICAL BURSTING AND INTRACELLULAR AND LUMINAL CALCIUM OSCILLATIONS IN INSULIN-SECRETING PANCREATIC BETA-CELLS

The extracellular calcium concentration has interesting effects on bur sting of pancreatic p-cells. The mechanism underlying the extracellula r Ca2+ effect is not well understood. By incorporating a low-threshold transient inward current to the store-operated bursting model of Chay , this paper elucidates the role of the extracellular Ca2+ concentrati on in influencing electrical activity, intracellular Ca2+ concentratio n, and the luminal Ca2+ concentration in the intracellular Ca2+ store. The possibility that this inward current is a carbachol-sensitive and TTX-insensitive Na+ current discovered by others is discussed. In add ition, this paper explains how these three variables respond when vari ous pharmacological agents are applied to the store-operated model.