β CELL MEMBRANE POTENTIAL AND INSULIN RELEASE; ROLE OF CALCIUM AND CALCIUM: MAGNESIUM RATIO

Abstract

Glucose‐induced insulin release from perfused rat pancreas was compared with glucose‐induced changes in membrane potential of β cells from mouse islets. Extracellular concentrations of Ca and Mg were varied as steps, simultaneously or separately, from 10% to 200% of normal in the presence of 11·1 mM glucose. A change in Ca induced a transient change in electrical activity paralleled by a transient change in insulin release. If the Ca/Mg ratio was maintained, steady‐state insulin release remained constant between 10% and 200% Ca, while electrical activity showed alterations. Analysis of burst parameters indicated that increased or decreased Ca entry was balanced by decreased or increased excitability. It is postulated that the β cell contains a compensator mechanism for the regulation of Ca influx. © 1983 The Physiological Society