Characterization of a large conductance non-selective anion channel in B lymphocytes
Abstract
Studies on ion channel currents in freshly isolated murine B lymphocytes with the patch clamp technique revealed the presence of a non-selective anion channel of large conductance in inside-out (i/o) patches. This channel is characterized here according to its unitary conductance, ion selectivity, regulatory factors, distribution and kinetic behaviour. With a unitary conductance of 348 +/- 4.4 pS in a normal physiological ion gradient, it exhibited an indiscriminate selectivity to cations (Na+ and K+). Selectivity to chloride over sodium was established by substitution of high concentrations of NaCl (450 mM) in the bath (i/o patches), resulting in a selectivity ratio (PCl/PNa) of 33. Selectivity to chloride over potassium was confirmed in a similar manner by substitution of TEA-Cl for KCl, yielding a selectivity ratio (PCl/Pk) greater than 80. Conductance of aspartate through the channel demonstrated the non-selective nature of this anion channel. Voltage proved to be a regulatory factor but other influences on channel activity were also present, including the configuration of the patch (channel is inactive in cell attached patches), and the enhancement of activity at negative membrane voltages by previous pulsing. Intracellula...Continue Reading
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