Large-conductance calcium-activated anion channel characteristics in neuroblastoma cells

Large-conductance anion channel characteristics were investigated in neurob lastoma cells (N2A) by using different configurations of the patch-clamp te chnique. In excised patches, the channel was induced by depolarising potent ials in 90% of experiments, had a conductance of 340 pS in symmetrical 135 mmol/l NaCl and exhibited the typical bell-shape activity. Neither the chan nel induction nor the channel activity was affected by rising the Ca2+ conc entration on the cytopasmic side of membranes. In cell-attached configurati on the maximal channel activity was shifted towards more positive potential s in comparison to that of excised patches and an increase in intracellular Ca2+, obtained by extracellular application of the Ca2+-ionophore A23187 i n the presence of 0.2 mu mol/l Ca2+, induced single-channel currents in 80% of patches compared to 31% of cell-attached experiments showing channel ac tivity in normal conditions. In turn, application of 2 mu mol/l Ca2+ induce d channel activity in 100% of patches. The reversal potential of the channe l in cell-attached patches was around -10 mV as the resting potential of ce lls eliciting channel activity. For cells where channel activity was not de tected in cell-attached mode, the resting potential was around -45 mV. Chan nel activity could be restored in most whole-cell recordings in the presenc e of 2 mu mol/l or more intracellular Ca2+ concentrations. The Ca2+-inducti on and the relation between channel activity and cell resting potential see m to suggest a role of the large-conductance anion channel in resting poten tial modulation during some basic functions of the neuroblastoma cell proli feration.