Mechanotransducer ion channels in chick skeletal muscle: the effects of extracellular pH.
Mechanotransducer ion channels in chick skeletal muscle: the effects of extracellular pH.
复制标题
鸡骨骼肌中的机械传导离子通道：细胞外 pH 值的影响。
DOI：
10.1113/jphysiol.1985.sp015699
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
Sachs,F
中科院分区：
文献类型：
--
作者：
Guharay,F;Sachs,F
组织培养的鸡胸肌的膜含有由膜张力激活的离子通道。在150 mM-外部K+和150 mM-内部Na+的情况下，通道的电导为70 pS，逆转电位为+30 mV。在150 mM-外部Na+和150 mM-内部K+（正常梯度）的情况下，通道的电导为35 pS，逆转电位为-30 mV。K+渗透性与Na+渗透性之比PK：PNa基于反转电位为4，基于电导为2。单通道记录的动力学分析表明，有一个开放（O）和三个封闭（C）状态。当根据线性序列模型C1-C2-C3-O 4进行分析时，发现只有控制C1-C2转变的速率常数（k1，2）受到拉伸或电压的影响。拉伸和电压对k1，2的影响可以总结为k1，2 = k1，2（0）exp（alpha V + theta P2），其中K1，2（0）是速率常数中与电压和拉伸无关的部分，alpha是电压灵敏度，V是跨膜电位，theta是拉伸灵敏度，P是施加的吸力。将细胞外pH从7.4增加到10.0以一种方式增加了α和θ，表明pK为9.1的位点滴定。N端氨基酸的单个赖氨酸可能负责调节电压和压力响应。细胞外pH不影响k1，2（0），即k1，2的电压和拉伸无关部分，表明pH在7.4 - 10范围内不会改变局部表面电荷。测定了s.a.通道不受pH影响，表明滴定位点不靠近通道口。
The membrane of tissue‐cultured chick pectoral muscle contains an ionic channel which is activated by membrane tension. With 150 mM‐external K+ and 150 mM‐internal Na+, the channel has a conductance of 70 pS and a reversal potential of +30 mV. With 150 mM‐external Na+ and 150 mM‐internal K+ (normal gradient) the channel has a conductance of 35 pS and a reversal potential of ‐30 mV. The ratio of K+ permeability to Na+ permeability, PK:PNa, is 4 based upon reversal potentials and is 2 based upon conductance. Kinetic analysis of single‐channel records indicates that there are one open (O) and three closed (C) states. When analysed according to a linear sequential model: C1‐C2‐C3‐O4, only the rate constant that governs the C1‐C2 transition (k1,2) is found to be affected by stretch or voltage. The effects of stretch and voltage on k1,2 can be summarized as k1,2 = k1,2(0) exp (alpha V + theta P2), where K1,2(0) is the voltage and stretch‐independent part of the rate constant, alpha is the voltage sensitivity, V is the transmembrane potential, theta is the stretch sensitivity and P is the applied suction. Increasing extracellular pH from 7.4 to 10.0 increases both alpha and theta in a manner suggesting titration of site(s) with a pK of 9.1. A single lysine of N‐terminal amino acid may be be responsible for modulating both the voltage and pressure responses. Extracellular pH does not affect k1,2(0), the voltage‐ and stretch‐independent part of k1,2, suggesting that pH in the range 7.4‐10 does not alter the local surface charge. The conductance and reversal potential of the s.a. channel are unaffected by pH, suggesting that the titrated site(s) is not close to the mouth of the channel.