Niemeyer M I, Hougaard C, Hoffmann E K, Jorgensen F, Stutzin A, Sepúlveda F V
Instituto de Ciencias Biomedicas, Facultad de Medicina, Universidad de Chile, Casilla 70058, Santiago-7, Chile.
J Physiol. 2000 May 1;524 Pt 3(Pt 3):757-67. doi: 10.1111/j.1469-7793.2000.00757.x.
The K+ and Cl- currents activated by hypotonic cell swelling were studied in Ehrlich ascites tumour cells using the whole-cell recording mode of the patch-clamp technique. Currents were measured in the absence of added intracellular Ca2+ and with strong buffering of Ca2+. K+ current activated by cell swelling was measured as outward current at the Cl- equilibrium potential (ECl) under quasi-physiological gradients. It could be abolished by replacing extracellular Na+ with K+, thereby cancelling the driving force. Replacement with other cations suggested a selectivity sequence of K+ > Rb+ > NH4 approximately Na+ approximately Li+; Cs+ appeared to be inhibitory. The current-voltage relationship of the volume-sensitive K+ current was well fitted with the Goldman-Hodgkin-Katz current equation between -130 and +20 mV with a permeability coefficient of around 10(-6) cm s(-1) with both physiological and high-K+ extracellular solutions. The class III antiarrhythmic drug clofilium blocked the volume-sensitive K+ current in a voltage-independent manner with an IC50 of 32 microM. Clofilium was also found to be a strong inhibitor of the regulatory volume decrease response of Ehrlich cells. Cell swelling-activated K+ currents of Ehrlich cells are voltage and calcium insensitive and are resistant to a range of K+ channel inhibitors. These characteristics are similar to those of the so-called background K+ channels. Noise analysis of whole-cell current was consistent with a unitary conductance of 5.5 pS for the single channels underlying the K+ current evoked by cell swelling, measured at 0 mV under a quasi-physiological K+ gradient.
利用膜片钳技术的全细胞记录模式，在艾氏腹水肿瘤细胞中研究了低渗性细胞肿胀激活的钾离子（K⁺）和氯离子（Cl⁻）电流。在不添加细胞内钙离子（Ca²⁺）并对Ca²⁺进行强缓冲的情况下测量电流。在准生理梯度下，将细胞肿胀激活的K⁺电流作为Cl⁻平衡电位（ECl）下的外向电流进行测量。用K⁺替代细胞外Na⁺可消除该电流，从而消除驱动力。用其他阳离子替代表明选择性顺序为K⁺＞Rb⁺＞NH₄⁺≈Na⁺≈Li⁺；Cs⁺似乎具有抑制作用。在-130至+20 mV之间，体积敏感性K⁺电流的电流-电压关系与戈德曼-霍奇金-卡茨电流方程拟合良好，在生理和高K⁺细胞外溶液中，渗透系数约为10⁻⁶ cm s⁻¹。Ⅲ类抗心律失常药物氯非铵以电压非依赖性方式阻断体积敏感性K⁺电流，IC50为32 μM。还发现氯非铵是艾氏细胞调节性体积减小反应的强抑制剂。艾氏细胞的细胞肿胀激活的K⁺电流对电压和钙不敏感，并且对一系列K⁺通道抑制剂具有抗性。这些特征与所谓的背景K⁺通道相似。在准生理K⁺梯度下于0 mV测量时，全细胞电流的噪声分析与细胞肿胀诱发的K⁺电流基础单通道的单位电导5.5 pS一致。
