McCann F V, McCarthy D C, Keller T M, Noelle R J
Department of Physiology, Dartmouth Medical School, Hanover, NH 03756.
Cell Signal. 1989;1(1):31-44. doi: 10.1016/0898-6568(89)90018-1.
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. Intracellular levels of calcium (i/o patches) did not appear to control channel conductances or regulate kinetic activity. Kinetic behaviour of this channel was complex, with periods of bursting and flickering activity interspersed with prolonged closed/open intervals. Multiple subconductance states were also present. The complex properties and behaviour of this channel suggest a possible role in signal transduction in B cell activation.
运用膜片钳技术对新鲜分离的小鼠B淋巴细胞中的离子通道电流进行研究，结果显示在反转（i/o）膜片中存在一种大电导的非选择性阴离子通道。在此，根据其单通道电导、离子选择性、调节因子、分布及动力学行为对该通道进行表征。在正常生理离子梯度下，其单通道电导为348±4.4 pS，对阳离子（Na⁺和K⁺）表现出无差别选择性。通过在浴槽（i/o膜片）中用高浓度NaCl（450 mM）替代，确立了对氯离子相对于钠离子的选择性，选择性比率（PCl/PNa）为33。通过用TEA-Cl替代KCl，以类似方式证实了对氯离子相对于钾离子的选择性，产生的选择性比率（PCl/Pk）大于80。天冬氨酸通过该通道的电导证明了此阴离子通道的非选择性性质。电压被证明是一种调节因子，但对通道活性也存在其他影响，包括膜片的构型（该通道在细胞贴附膜片中无活性），以及通过先前的脉冲在负膜电压下增强活性。细胞内钙水平（i/o膜片）似乎并不控制通道电导或调节动力学活性。该通道的动力学行为复杂，有爆发和闪烁活动期，其间穿插着较长的关闭/开放间隔。还存在多个亚电导状态。该通道复杂的特性和行为表明其在B细胞激活的信号转导中可能发挥作用。
