Sims S M, Kelly M E, Dixon S J
Department of Physiology, University of Western Ontario, London, Canada.
Pflugers Arch. 1991 Oct;419(3-4):358-70. doi: 10.1007/BF00371118.
Membrane electrical properties of freshly isolated rat osteoclasts were studied using patch-clamp recording methods. Characterization of the passive membrane properties indicated that the osteoclast cell membrane behaved as an isopotential surface. The specific membrane capacitance was 1.2 +/- 0.3 microF/cm2 (mean +/- SD), with no difference between cells plated on glass and those adhering to a permeable collagen substrate. The current/voltage (I/V) relationship of all cells showed inward rectification and I/V curves shifted 51 mV positive per tenfold increase of [K+]out, indicating an inwardly rectifying K+ conductance. The voltage dependence of the K+ chord conductance (gK) also shifted positive along the voltage axis, and the maximum conductance increased, with elevation of [K+]out. gK for cells bathed in 4.7 mM [K+]out increased e-fold per 12 mV hyperpolarization, and half-maximal activation was at -89 mV. Approximately 18% (50 pS/pF) of the maximum gK was active at -70 mV. Inward single-channel currents were recorded in cell-attached patches at hyperpolarizing potentials. With symmetrical K+, channel conductance was 25 +/- 3 pS and reversal was close to the K+ equilibrium potential, consistent with this K+ channel underlying the whole-cell K+ currents. With both conventional whole-cell and perforated-patch recording, no voltage-activated Ca2+ current was detected. In approximately 30% of osteoclasts studied, an outwardly rectifying current was observed, which was reversibly blocked by 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid (SITS). This DIDS- and SITS-sensitive current reversed direction at the chloride equilibrium potential. We conclude that an inwardly rectifying K+ current is present in all rat osteoclasts and that some osteoclasts also exhibit an outwardly rectifying Cl- current. Both these membrane conductances may play an important physiological role by dissipating the potential that arises from the electrogenic transport of H+ across the ruffled membrane of the osteoclast.
采用膜片钳记录方法研究了新鲜分离的大鼠破骨细胞的膜电特性。对被动膜特性的表征表明，破骨细胞膜表现为等电位表面。比膜电容为1.2±0.3微法/平方厘米（平均值±标准差），接种在玻璃上的细胞与附着在可渗透胶原底物上的细胞之间无差异。所有细胞的电流/电压（I/V）关系均显示内向整流，且随着细胞外[K⁺]每增加10倍，I/V曲线正向移动51毫伏，表明存在内向整流钾电导。随着细胞外[K⁺]升高，钾弦电导（gK）的电压依赖性也沿电压轴正向移动，且最大电导增加。在细胞外[K⁺]为4.7毫摩尔的条件下，细胞的gK每超极化12毫伏增加e倍，半数最大激活电位为-89毫伏。在-70毫伏时，约18%（50皮安/皮法）的最大gK处于激活状态。在超极化电位下，于细胞贴附式膜片中记录到内向单通道电流。在钾离子对称的情况下，通道电导为25±3皮安，反转电位接近钾离子平衡电位，这与该钾通道构成全细胞钾电流的基础一致。采用传统全细胞膜片钳记录和穿孔膜片钳记录时，均未检测到电压激活的钙离子电流。在约30%所研究的破骨细胞中，观察到一种外向整流电流，该电流可被4,4'-二异硫氰基芪-2,2'-二磺酸（DIDS）和4-乙酰氨基-4'-异硫氰基芪-2,2'-二磺酸（SITS）可逆性阻断。这种对DIDS和SITS敏感的电流在氯离子平衡电位处反转方向。我们得出结论，所有大鼠破骨细胞均存在内向整流钾电流，且部分破骨细胞还表现出外向整流氯电流。这两种膜电导可能通过耗散破骨细胞皱襞膜上氢离子电转运产生的电位而发挥重要的生理作用。
