Influence on Anion Transport on Glucose-induced Electrical Activity in the B-Cell

We have previously shown that the effect of glucose on electrical activity (EA) in islet B-cells is altered by modification of pH. The regulation of intracellular pH (pH_i) in nerve and muscle cells is coupled to anion exchange. In the present study we have examined the involvement of HCO₃:Cl exchange across the plasma membrane in the maintenance of glucose-induced EA in B-cells. 4,4′-diisothiocyanostilbene-2,2′ disulfonic acid (DIDS), an inhibitor of anion exchange, elicited a dose-related stimulation of EA in the presence of 11.1 mM glucose. The increase in the relative duration of the active phase (constant spike activity) was first observed at 20 μM DIDS, and a nearly maximal effect was obtained at 200 μM. The substitution of HCO₃⁻ by a Hepes buffer elicited constant spike activity. The application of 0.25 μM tributyltin, an electroneutral Cl:OH exchanger, also enhanced EA as indicated by an increase in the duration of the active phase. The influence of HCO₃⁻ withdrawal, DIDS, and tributyltin all elicited electrical events similar to that obtained by a decrease in pH_i. Our results suggest that anion exchange may be involved in the regulation of electrical events in the B-cell by influencing pH_i, as has been documented to occur in invertebrate nerve and muscle.