Voltage dependence of transient and steady-state Na/K pump currents in myocytes.
Voltage dependence of transient and steady-state Na/K pump currents in myocytes.
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肌细胞中瞬态和稳态 Na/K 泵电流的电压依赖性。
DOI：
10.1007/bf00220766
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发表时间：
1989
影响因子：
4.3
通讯作者：
Bahinski,A
中科院分区：
文献类型：
--
作者：
Gadsby,DC;Nakao,M;Bahinski,A
本文回顾了实验，其中 Na/K 泵电流被确定为豚鼠心室肌细胞中的旋花草苷敏感电流，通过宽头移液器进行电压钳位和内部透析。在 150 mM 细胞外 [Na] 存在的情况下，分别在正向和反向 Na/K 交换过程中，向外和向内泵电流均强烈依赖于电压。但外部 [Na] 减少至 1.5 mM 严重削弱了外部 Na/K 泵浦电流的电压灵敏度。在正向或反向 Na/K 交换期间，或者当泵活动仅限于 Na 易位步骤时，电压跃变会引发大的瞬态泵电流，但当泵可能参与 K/K 交换时则不会。这些发现表明，Na 易位（而非 K 易位）涉及通过膜场的净电荷运动，并且正向和反向 Na/K 传输循环的速率限制不是由电压敏感步骤而是由随后的电压不敏感步骤限制。
Experiments are reviewed here in which Na/K pump current was determined as strophanthidin-sensitive current in guinea-pig ventricular myocytes, voltage-clamped and internally-dialyzed via wide-tipped pipettes. In the presence of 150 mM extracellular [Na], both outward and inward pump current, during forward and reverse Na/K exchange respectively, were strongly voltage dependent. But reduction of external [Na] to 1.5 mM severely attenuated the voltage sensitivity of outward Na/K pump current. Voltage jumps elicited large transient pump currents during forward or reverse Na/K exchange, or when pump activity was restricted to Na translocation steps, but not when pumps were presumably engaged in K/K exchange. These findings indicate that Na translocation, butnotK translocation, involves net charge movement through the membrane field, and that both forward and reverse Na/K transport cycles are rate-limited not by that voltage-sensitive step but by a subsequent voltage-insensitive step.