Study of a glucose-activated anion-selective channel in rat pancreatic β-cells

Abstract.

Cell-attached channel recordings were made of an inward channel current in isolated rat pancreatic β-cells incubated in the presence of diazoxide to clamp the membrane potential close to the K⁺ equilibrium potential. With 42 mM Cl^– in the pipette solution, a channel of approximately 200 pS was observed in 20–40% of patches which conducted an inward current at a pipette potential of 0 mV. The channel was activated by a rise in glucose concentration over the range 5–20 mM. The channel was also activated by methylglyoxal, possibly due to its metabolism to D-lactate, but not by the non-metabolizable glucose analogue 3-O-methyl glucose. The channel was activated by hypotonic cell swelling and was sensitive to inhibition by the anion channel blockers 4,4'-dithiocyanatostilbene-2,2'-disulphonic acid, 5-nitro-2-(3-phenylpropylamino) benzoic acid and 4-hydroxytamoxifen. Current reversal occurred at a pipette potential of approximately –67 mV. Raising [Cl^–] in the pipette solution to 142 mM shifted the reversal potential to –52 mV. It is suggested that the channel is the volume-sensitive anion channel previously described in insulin-secreting cells. Activation of the channel by glucose could be important in generating a depolarizing current leading to increased electrical activity and insulin release, particularly at higher concentrations of glucose where K_ATP channel activity is minimal.