Bahinski A, Nakao M, Gadsby D C
Laboratory of Cardiac Physiology, Rockefeller University, New York, NY 10021-6399.
Proc Natl Acad Sci U S A. 1988 May;85(10):3412-6. doi: 10.1073/pnas.85.10.3412.
The voltage dependence of steady and transient changes in Na+/K+ pump current, in response to step changes in membrane potential, was investigated in guinea pig ventricular myocytes voltage clamped and internally dialyzed under experimental conditions designed to support four separate modes of Na+/K+ pump activity. Voltage jumps elicited transient pump currents when the pump cycle was running forward or backward, or when pumps were limited to Na+ translocation, but not when they were made to carry out K+/K+ exchange. This result indicates that K+ translocation involves no net charge movement across the membrane field and is therefore voltage insensitive. The transient pump currents seen during Na+/K+ transport demonstrate that both forward and reverse pump cycles are rate limited not by the voltage-dependent step but by a voltage-independent step, probably K+ translocation. These findings severely constrain kinetic models of Na+/K+ pump activity.
在豚鼠心室肌细胞中，于电压钳制并内部透析的实验条件下，研究了在支持钠钾泵四种不同活动模式的条件下，膜电位阶跃变化时钠钾泵电流稳态和瞬态变化的电压依赖性。当泵循环正向或反向运行时，或者当泵仅限于钠转运时，电压阶跃会引发瞬态泵电流，但当它们进行钾/钾交换时则不会。这一结果表明，钾转运不涉及跨膜电场的净电荷移动，因此对电压不敏感。在钠钾转运过程中观察到的瞬态泵电流表明，正向和反向泵循环的速率限制不是由电压依赖性步骤，而是由一个电压非依赖性步骤（可能是钾转运）决定的。这些发现严重限制了钠钾泵活动的动力学模型。
