Large-conductance calcium-activated anion channel characteristics in neuroblastoma cells.
Large-conductance anion channel characteristics were investigated in neuroblastoma cells (N2A) by using different configurations of the patch-clamp technique. In excised patches, the channel was induced by depolarising potentials 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 channel induction nor the channel activity was affected by rising the Ca2+ concentration on the cytopasmic side of membranes. In cell-attached configuration the maximal channel activity was shifted towards more positive potentials in comparison to that of excised patches and an increase in intracellular Ca2+, obtained by extracellular application of the Ca2+-ionophore A23187 in the presence of 0.2 micromol/l Ca2+, induced single-channel currents in 80% of patches compared to 31% of cell-attached experiments showing channel activity in normal conditions. In turn, application of 2 micromol/l Ca2+ induced channel activity in 100% of patches. The reversal potential of the channel in cell-attached patches was around -10 mV as the resting potential of cells eliciting channel activity. For cells where channel activity was not detected in cell-attached mode, the resting potential was around -45 mV. Channel activity could be restored in most whole-cell recordings in the presence of 2 micromol/l or more intracellular Ca2+ concentrations. The Ca2+-induction and the relation between channel activity and cell resting potential seem to suggest a role of the large-conductance anion channel in resting potential modulation during some basic functions of the neuroblastoma cell proliferation.
Nobile
M
M
Istituto di Cibernetica e Biofisica, CNR, Genova, Italy. nobile@icb.ge.cnr.it
Lagostena
L
L
D000818:Animals; D000838:Anions; D000001:Calcimycin / Q000494:pharmacology; D015220:Calcium Channels / Q000737:chemistry* / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D009447:Neuroblastoma / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D012965:Sodium Chloride / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured
D000838:Anions; D015220:Calcium Channels; D007476:Ionophores; D000001:Calcimycin; D012965:Sodium Chloride