Reeves W B, Andreoli T E
Department of Internal Medicine, University of Arkansas College of Medicine, Little Rock 72205.
J Membr Biol. 1990 Jan;113(1):57-65. doi: 10.1007/BF01869606.
The present studies examined some of the properties of Cl- channels in renal outer medullary membrane vesicles incorporated into planar lipid bilayers. The predominant channel was anion selective having a PCl/PK ratio of 10 and a unit conductance of 93 pS in symmetric 320 mM KCl. In asymmetric KCl solutions, the I-V relations conformed to the Goldman-Hodgkin-Katz equation. Channel activity was voltage-dependent with a gating charge of unity. This voltage dependence of channel activity may account, at least in part, for the striking voltage dependence of the basolateral membrane Cl- conductance of isolated medullary thick ascending limb segments. The Cl- channels incorporated into the planar bilayers were asymmetrical: the trans surface was sensitive to changes in ionized Ca2+ concentrations and insensitive to reducing KCl concentrations to 10 mM, while the cis side was insensitive to changes in ionized Ca2+ concentrations, but was inactivated by reducing KCl concentrations to 50 mM.
本研究检测了整合到平面脂双层中的肾外髓质膜囊泡中氯离子通道的一些特性。主要通道具有阴离子选择性，在对称的320 mM KCl中，PCl/PK比值为10，单位电导为93 pS。在非对称KCl溶液中，电流-电压关系符合戈德曼-霍奇金- Katz方程。通道活性具有电压依赖性，门控电荷为1。通道活性的这种电压依赖性可能至少部分解释了离体髓袢升支粗段基底外侧膜氯离子电导显著的电压依赖性。整合到平面双层中的氯离子通道是不对称的：跨膜面离子化钙浓度变化敏感，将KCl浓度降至10 mM不敏感，而顺膜面离子化钙浓度变化不敏感，但将KCl浓度降至50 mM会使其失活。
