THE EFFECT OF INTRACELLULAR PH ON ATP-DEPENDENT POTASSIUM CHANNELS OF FROG SKELETAL-MUSCLE
THE EFFECT OF INTRACELLULAR PH ON ATP-DEPENDENT POTASSIUM CHANNELS OF FROG SKELETAL-MUSCLE
复制标题
DOI：
10.1113/jphysiol.1992.sp018939
复制
发表时间：
1992-01-01
影响因子：
5.5
通讯作者：
STANFIELD, PR
中科院分区：
文献类型：
--
作者：
DAVIES, NW;STANDEN, NB;STANFIELD, PR
1. 我们采用膜片钳技术研究了蛙（Rana temporaria）骨骼肌细胞膜细胞质表面pH值对ATP依赖性K+通道（K（ATP）channels）的影响，并研究了ATP结合动力学. 在没有ATP的情况下，pH值的降低导致单通道电流幅度略有下降，非常短暂的关闭次数增加，表观平均开放时间增加，以及爆发持续时间增加。 在对错过的关闭进行校正后，平均开放时间的变化很小。 尽管这些变化的详细动力学，通道开放状态的概率，P（开放），改变pH值的变化，在ATP的情况下。 在存在ATP的情况下，内部pH值（pH（i））的降低降低了ATP对通道的抑制程度，使P（开放）和[ATP]相关曲线向更高浓度的ATP移动，而不改变其陡度。 通道活性（K（i））半抑制的ATP浓度在pH 7.2时为17 μ M，在pH 6.3.4时为260 μ M。 pH值的影响可以通过假设一个或两个质子结合到通道并阻止ATP结合以发挥其导致通道关闭的作用来建模。 ATP和H+的预测解离常数分别为5.4和0.11 μ M。 结合和解离ATP的速率常数由平均开放时间对[ATP]的依赖性和K（i）估算。 ATP结合的表观速率常数分别为0.6和0.04 mM-1 ms-1，在pH 7.2和6.3，而未结合的速率常数为0.01 ms-1。 根据我们的模型，计算出的ATP结合的真实速率常数为1.85 mM-1 ms-1。 ATP结合也导致爆发持续时间的减少。 这里描述的pH值的影响与心肌和胰腺B细胞中的发现不同。 结果进行了讨论，在运动过程中的骨骼肌K（ATP）通道的可能功能。
1. We have used patch-clamp methods to study the effects of pH at the cytoplasmic surface of the membrane on ATP-dependent K+ channels (K(ATP) channels) in patches excised from frog (Rana temporaria) skeletal muscle, and to study the kinetics of ATP binding.2. In the absence of ATP, a reduction in pH led to a slight decrease in single-channel current amplitude, an increase in the number of very brief closings, an increase in the apparent mean open time, and an increase in burst duration. After correction for missed closings, the change in mean open time was slight. Despite these changes in detailed kinetics, the channel open-state probability, P(open), changed little with changes in pH in the absence of ATP.3. In the presence of ATP, a decrease in internal pH (pH(i)) reduced the degree of channel inhibition by ATP, shifting the curve relating P(open) and [ATP] to higher concentrations of ATP without altering its steepness. The ATP concentration for half-inhibition of channel activity (K(i)) was 17-mu-M at pH 7.2 and 260-mu-M at pH 6.3.4. The effect of pH could be modelled by assuming that one or two protons bind to the channel and prevent ATP binding to exert its effect of causing channel closure. The predicted dissociation constants for ATP and H+ respectively were 5.4 and 0.11-mu-M.5. The rate constants for binding and unbinding of ATP were estimated from the dependence of the mean open time on [ATP] and from the K(i). The apparent rate constants for ATP binding were 0.6 and 0.04 mM-1 ms-1 at pH 7.2 and 6.3 respectively, while the rate constant for unbinding was 0.01 ms-1. In terms of our model the calculated true rate constant for ATP binding was 1.85 mM-1 ms-1. ATP binding also led to a reduction in burst duration.6. The effect of pH described here differs from findings in cardiac muscle and pancreatic B-cells. The results are discussed in relation to the possible function of K(ATP) channels in skeletal muscle during exercise.