Hallani M, Lynch J W, Barry P H
School of Physiology and Pharmacology, University of New South Wales, Sydney, Australia.
J Membr Biol. 1998 Jan 15;161(2):163-71. doi: 10.1007/s002329900323.
We investigated the properties of calcium-activated chloride channels in inside-out membrane patches from the dendritic knobs of acutely dissociated rat olfactory receptor neurons. Patches typically contained large calcium-activated currents, with total conductances in the range 30-75 nS. The dose response curve for calcium exhibited an EC50 of about 26 microM. In symmetrical NaCl solutions, the current-voltage relationship reversed at 0 mV and was linear between -80 and +70 mV. When the intracellular NaCl concentration was progressively reduced from 150 to 25 mM, the reversal potential changed in a manner consistent with a chloride-selective conductance. Indeed, modeling these data with the Goldman-Hodgkin-Katz equation revealed a PNa/PCl of 0.034. The halide permeability sequence was PCl > PF > PI > PBr indicating that permeation through the channel was dominated by ion binding sites with a high field strength. The channels were also permeable to the large organic anions, SCN-, acetate-, and gluconate-, with the permeability sequence PCl > PSON > Pacetate > Pgluconate. Significant permeation to gluconate ions suggested that the channel pore had a minimum diameter of at least 5.8 A.
我们研究了急性分离的大鼠嗅觉受体神经元树突棘上内向外膜片钳中钙激活氯离子通道的特性。膜片通常包含大的钙激活电流，总电导范围为30 - 75 nS。钙的剂量反应曲线显示EC50约为26 μM。在对称的NaCl溶液中，电流 - 电压关系在0 mV处反转，并且在 - 80至 + 70 mV之间呈线性。当细胞内NaCl浓度从150 mM逐渐降低到25 mM时，反转电位的变化方式与氯离子选择性电导一致。实际上，用戈德曼 - 霍奇金 - 凯茨方程对这些数据进行建模显示PNa/PCl为0.034。卤化物通透性顺序为PCl > PF > PI > PBr，表明通过该通道的通透主要由具有高场强的离子结合位点主导。这些通道也可通透大的有机阴离子SCN-、乙酸根和葡萄糖酸根，通透性顺序为PCl > PSON > Pacetate > Pgluconate。对葡萄糖酸根离子的显著通透表明通道孔的最小直径至少为5.8 Å。
