Kelly M E, Dixon S J, Sims S M
Department of Physiology, University of Western Ontario, London, Canada.
J Membr Biol. 1992 Mar;126(2):171-81. doi: 10.1007/BF00231915.
Ionic conductances of rabbit osteoclasts were investigated using both whole-cell and cell-attached configurations of the patch-clamp recording technique. The predominant conductance found in these cells was an inwardly rectifying K+ conductance. Whole-cell currents showed an N-shaped current-voltage (I-V) relation with inward current activated at potentials negative to EK. When external K+ was varied, I-V curves shifted 53 mV/10-fold change in [K+]out, as predicted for a K(+)-selective channel. Inward current was blocked by Ba2+ and showed a time-dependent decline at negative potentials, which was reduced in Na(+)-free external solution. Inward single-channel currents were recorded in the cell-attached configuration. Single-channel currents were identified as inward-rectifier K+ channels based on the following observations: (i) Unitary I-V relations rectified, with only inward current resolved. (ii) Unitary conductance (gamma) was 31 pS when recorded in the cell-attached configuration with 140 mM K+ in the pipette and was found to be dependent on [K+]. (iii) Addition of Ba2+ to the pipette solution abolished single-channel events. We conclude that rabbit osteoclasts possess inwardly rectifying K+ channels which give rise to the inward current recorded at negative potentials in the whole-cell configuration. This inwardly rectifying K+ current may be responsible for setting the resting membrane potential and for dissipating electrical potential differences which arise from electrogenic transport of protons across the osteoclast ruffled border.
利用膜片钳记录技术的全细胞和细胞贴附模式，对兔破骨细胞的离子电导进行了研究。在这些细胞中发现的主要电导是内向整流钾离子电导。全细胞电流呈现出N形电流-电压（I-V）关系，内向电流在负于EK的电位下被激活。当外部钾离子浓度变化时，I-V曲线随着[K⁺]out每10倍变化而移动53 mV，这与钾离子选择性通道的预测一致。内向电流被钡离子阻断，并且在负电位下呈现出时间依赖性衰减，在无钠的外部溶液中这种衰减会减小。在细胞贴附模式下记录到了内向单通道电流。基于以下观察结果，单通道电流被鉴定为内向整流钾离子通道：（i）单通道I-V关系呈整流性，仅分辨出内向电流。（ii）当在吸管中含有140 mM钾离子的细胞贴附模式下记录时，单通道电导（γ）为31 pS，并且发现其依赖于[K⁺]。（iii）向吸管溶液中添加钡离子消除了单通道事件。我们得出结论，兔破骨细胞拥有内向整流钾离子通道，该通道在全细胞模式下负电位时产生内向电流。这种内向整流钾离子电流可能负责设定静息膜电位，并消散因质子跨破骨细胞皱襞缘的电致转运而产生的电位差。
