Ionic Mechanisms of the Glucose-induced Membrane Potential Changes in B-cells

The ionic basis of the glucose-induced membrane potential changes in pancreatic B-cells was investigated. The results suggest that the initial depolarization of the membrane in response to a stimulation with glucose is due to a decrease of the K permeability. This depolarization seems to open a voltage-dependent Ca-channel and thereby an additional depolarization, the depolarization phase of the slow waves, is initiated. Insulin release is then triggered by the entering Ca ions. The fast spike activity may be a consequence of the exocytotic process. The polarization phase of the slow waves seems to be caused by the activity of an electrogenic Na-K-pump and a calcium-dependent increase of the K permeability. The activity of the Na-pump is considered to be regulated by the intracellular Na concentration.