Kawahara K, Hunter M, Giebisch G
Am J Physiol. 1987 Sep;253(3 Pt 2):F488-94. doi: 10.1152/ajprenal.1987.253.3.F488.
Potassium channels from the apical and basolateral membranes of Necturus proximal tubule were studied using the patch-clamp technique. The conductance of the basolateral channel was dependent on the pipette K+ concentration (apparent Km, 65.5 mM K+; maximum channel conductance, 49.8 pS). The permeability ratio (PK+/PNa+) was approximately 10:1. The fractional open time increased with hyperpolarization, whereas mean open times did not change. Ba2+ (0.1 mM pipette concentration) blocked the channel and reduced the mean open time. The apical K+ channel was activated with depolarization and had a slope conductance of 60 pS in the inside-out configuration (100 mM KCl in the pipette and 2.5 mM KCl in the bath). The K+-Na+ selectivity ratio was 32:1. These different channel types will allow independent control of the apical and basolateral membrane K+ conductances.
利用膜片钳技术研究了美西螈近端小管顶端和基底外侧膜的钾通道。基底外侧通道的电导取决于微电极内的钾离子浓度（表观米氏常数，65.5 mM K⁺；最大通道电导，49.8 pS）。通透率（PK⁺/PNa⁺）约为10:1。开放时间分数随超极化增加，而平均开放时间不变。Ba²⁺（微电极浓度0.1 mM）阻断通道并缩短平均开放时间。顶端钾通道在去极化时被激活，在内外翻转模式下（微电极内100 mM KCl，浴槽内2.5 mM KCl）斜率电导为60 pS。钾 - 钠选择性比为32:1。这些不同类型的通道将允许对顶端和基底外侧膜的钾电导进行独立控制。
