Ionic determinants of bioelectrical spiking activity in the pancreatic B-cell.

A rise in extracellular glucose concentration from 8.3 to 16.7 mM stimulates both Ca2+ inflow and K+ exit in perfused rat pancreatic islets. These ionic changes are associated with an increase in bioelectrical spiking activity. From a quantitative analysis of 45Ca and 86Rb outflow from prelabelled islets, it is proposed that each electrical spike coincides, approximately, with the entry of 0.8 fmol of Ca2+ and exit of 3.6 fmol of K+ per mm2 of cell surface.