Wilson Jim R, Duncan Neil A, Giles Wayne R, Clark Robert B
Department of Civil Engineering and Joint Injury and Arthritis Research Group, The University of Calgary, Calgary, Alberta, Canada T2N 4N1.
J Physiol. 2004 May 15;557(Pt 1):93-104. doi: 10.1113/jphysiol.2003.058883. Epub 2004 Mar 12.
The electrophysiological properties of acutely isolated canine articular chondrocytes have been characterized using patch-clamp methods. The 'steady-state' current-voltage relationship (I-V) of single chondrocytes over the range of potentials from -100 to +40 mV was highly non-linear, showing strong outward rectification positive to the zero-current potential. Currents activated at membrane potentials negative to -50 mV were time independent, and the I-V from -100 to -60 mV was linear, corresponding to an apparent input resistance of 9.3 +/- 1.4 G Omega (n= 23). The outwardly rectifying current was sensitive to the K(+) channel blocking ion tetraethylammonium (TEA), which had a 50% blocking concentration of 0.66 mM (at +50 mV). The 'TEA-sensitive' component of the outwardly rectifying current had time- and membrane potential-dependent properties, activated near -45 mV and was half-activated at -25 mV. The reversal potential of the 'TEA-sensitive' current with external K(+) concentration of 5 mm and internal concentration of 145 mM, was -84 mV, indicating that the current was primarily carried by K(+) ions. The resting membrane potential of isolated chondrocytes (-38.1 +/- 1.4 mV; n= 19) was depolarized by 14.8 +/- 0.9 mV by 25 mM TEA, which completely blocked the K(+) current of these cells. These data suggest that this voltage-sensitive K(+) channel has an important role in regulating the membrane potential of canine articular chondrocytes.
采用膜片钳方法对急性分离的犬关节软骨细胞的电生理特性进行了表征。在-100至+40 mV电位范围内，单个软骨细胞的“稳态”电流-电压关系（I-V）高度非线性，在零电流电位正向呈现出强烈的外向整流。在膜电位负于-50 mV时激活的电流与时间无关，且-100至-60 mV的I-V呈线性，对应表观输入电阻为9.3±1.4 GΩ（n = 23）。外向整流电流对钾（K⁺）通道阻断离子四乙铵（TEA）敏感，其在+50 mV时的50%阻断浓度为0.66 mM。外向整流电流的“TEA敏感”成分具有时间和膜电位依赖性特性，在-45 mV附近激活，在-25 mV时半激活。在外部K⁺浓度为5 mM和内部浓度为145 mM时，“TEA敏感”电流的反转电位为-84 mV，表明该电流主要由K⁺离子携带。分离软骨细胞的静息膜电位（-38.1±1.4 mV；n = 19）被25 mM TEA去极化14.8±0.9 mV，这完全阻断了这些细胞的K⁺电流。这些数据表明，这种电压敏感性K⁺通道在调节犬关节软骨细胞的膜电位中起重要作用。
