对单价和二价阳离子具有通透性的通道的离子电流。
Ionic currents of channels that are permeable to monovalent and divalent cations.
作者信息
Oosawa Y
机构信息
Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, Japan.
出版信息
Biophys J. 1989 Dec;56(6):1217-23. doi: 10.1016/S0006-3495(89)82768-7.
The cation-selective channel from Tetrahymena cilia is permeable to both monovalent and divalent cations. The single channel conductance in mixed solutions of K+ and Ca2+ was determined by the Gibbs-Donnan ratio of K+ and Ca2+, and the binding sites of this channel were considered to be always occupied by two potassium ions or by one calcium ion under the experimental conditions: 5-90 mM K+ and 0.5-35 mM Ca2+ (Oosawa and Kasai, 1988). A two-barrier model for the channel was introduced and the values of Michaelis-Menten constants and maximum currents carried by K+ and Ca2+ were calculated using this model. Single channel current amplitudes and reversal potentials were calculated from these values. The calculated single-channel currents were compared with those obtained experimentally. The calculated reversal potentials were compared with the resting potentials of Tetrahymena measured in various concentrations of extracellular K+ and Ca2+. The method of calculation of ionic currents and reversal potentials presented here is helpful for understanding the properties of the channels permeable to both monovalent and divalent cations.
来自四膜虫纤毛的阳离子选择性通道对单价和二价阳离子均具有通透性。钾离子（K⁺）和钙离子（Ca²⁺）混合溶液中的单通道电导由K⁺和Ca²⁺的吉布斯-唐南比率决定，并且在5 - 90 mM K⁺和0.5 - 35 mM Ca²⁺的实验条件下，该通道的结合位点被认为总是被两个钾离子或一个钙离子占据（大泽和笠井，1988年）。引入了该通道的双势垒模型，并使用该模型计算了米氏常数以及K⁺和Ca²⁺携带的最大电流值。根据这些值计算了单通道电流幅度和反转电位。将计算得到的单通道电流与实验测得的电流进行比较。将计算得到的反转电位与在不同细胞外K⁺和Ca²⁺浓度下测得的四膜虫静息电位进行比较。这里介绍的离子电流和反转电位的计算方法有助于理解对单价和二价阳离子均具有通透性的通道的特性。
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