title: Anion and cation permeability of a large conductance anion channel in the T84 human colonic cell line.
abstract: A large conductance multi-state channel was identified and characterized in single channel recordings from cell-attached and excised patches of the human colonic tumor cell line, T84. The channel activity was dependent on the presence of both permeable cations and anions. In Na(+)-free symmetrical Cl- solutions or Cl(-)-free symmetrical Na+ solutions the channel was inactive. Addition of 5 mM NaCl (NaI or KCl) induced channel activity. The selectivity sequence obtained from the shift in reversal potential was I- (1.9) > Cl- (1) > Na+ (0.5) > K+ (0.3). SO2-(4), SCN- (thiocyanate) and NMDG+ were impermeant. Multiple subconductance states were identified at all voltages explored (+/- 90 mV). The minimum conductance encountered in symmetrical 100 mM NaCl was a 15 pS substrate, the maximum, 210 pS. The channel appeared to be composed of multiples of the 15 pS subunits which were reversibly blocked by the loop diuretic bumetanide (5 microM).
mesh_terms: D000838:Anions / Q000378:metabolism; D002034:Bumetanide / Q000494:pharmacology; D002412:Cations / Q000378:metabolism; D003110:Colonic Neoplasms / Q000378:metabolism; D004553:Electric Conductivity; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D010539:Permeability; D010766:Phosphorylation; D014407:Tumor Cells, Cultured / Q000378:metabolism*
chemical_list: D000838:Anions; D002412:Cations; D007473:Ion Channels; D002034:Bumetanide