Glucose-induced decrease in Rb⁺ permeability in pancreatic β cells

Abstract

THE membrane potential of pancreatic islet cells varies with the extracellular D-glucose concentration¹, from about −33 mV at zero glucose to about −16 mV at 28 mM, and 3–17 mM D-glucose induces bursts of rhythmic depolarisations with an amplitude of a few mV. Similar observations have been obtained², but with a membrane potential of about −60 mV in the absence of glucose. Comparisons of various sugars revealed a qualitative correlation between depolarising and insulin-releasing capacities¹; continuous recordings from single islet cells revealed a quantitative correlation between spike frequency and D-glucose concentration^2,3. Depolarisation of the β-cell membrane may therefore be essential for the triggering of insulin secretion^1–3. We report some experiments which indicate that the diminishing effect of D-glucose on membrane potential may be caused by a decrease in K⁺ permeability.