EFFECTS OF MEMBRANE POTENTIAL ON SODIUM AND POTASSIUM FLUXES IN SQUID AXONS
EFFECTS OF MEMBRANE POTENTIAL ON SODIUM AND POTASSIUM FLUXES IN SQUID AXONS
复制标题
膜电位对鱿鱼轴突中钠和钾通量的影响
DOI：
10.1111/j.1749-6632.1974.tb19106.x
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发表时间：
1974
影响因子：
5.2
通讯作者：
L. Mullins
中科院分区：
文献类型：
--
作者：
F. Brinley;L. Mullins
大多数可兴奋细胞的跨膜电位差为50至100 mV（负电位）。虽然这个电位差的绝对值可能看起来相当小，但它发生在如此极薄的界面上，以至于所得电场（100，000 V/cm）接近许多脂质材料的介电击穿点。由于膜的许多成分是带电粒子或极性分子，它们在膜中的取向可能会受到这种大的电位梯度的影响，并且似乎可以合理地假设负责离子传输的大分子以及传输系统的参数，例如幅度和/或对内部和外部离子的灵敏度也可能是场强的函数。将要描述的实验被设计为通过以两种方式改变跨膜的电位梯度来测试该假设：（1）通过使超极化电流穿过膜和（2）通过改变[ K ] i或[ K ] o，已知这些程序改变膜电位，因为膜对该离子是高度可渗透的。关于超极化对头足类轴突钠外流的影响的简要报道已经出现。除了电场可能预期对任何极性大分子具有的一般定向效应之外，膜电位可能对鱿鱼轴突中的Na：K转运具有特定效应，因为泵的产电特性（泵操作的一个循环向外移动的正电荷多于向内移动的正电荷）。因为泵送从电池挤出净电荷，所以改变电势梯度必须改变泵每个循环所做的功的量，并且因此可能预期改变泵送的速率（即，Na或K通量的大小）或它们对外部离子的敏感性。
The potential difference across the membranes of most excitable cells is of the order of 50 to 100 mV inside negative. Although this potential difference may seem rather small in absolute magnitude, it occurs across an interface of such extreme thinness that the resultant electric field ( 1 00,000 V/cm) approaches the dielectric breakdown point of many lipid materials. Since many of the constituents of the membrane are either charged particles or polar molecules, their orientation in the membrane might be affected by the presence of such large potential gradients, and it seems reasonable to suppose that the macromolecules responsible for ion transport as well as parameters of the transport system such as magnitude and/or sensitivity to internal and external ions might also be a function of the field strength. The experiments to be described were designed to test this hypothesis by altering the potential gradient across the membrane in two ways: (1 ) by passing hyperpolarizing electrical currents across the membrane and (2) by changing [ K ] i or [ K ] o , procedures that are known to change the membrane potential since the membrane is highly permeable to this ion. Brief reports of the effects of hyperpolarizations on sodium efflux from cephalopod axons have appeared p r e v i o ~ s l y . ~ * ' ~ In addition to the general orienting effect that an electrical field might be expected to have on any polar macromolecule, membrane potential might have a specific effect on Na : K transport in squid axons because of the electrogenic character of the pump (one cycle of pump operation moves more positive charges outward than inward). Because pumping extrudes a net charge from the cell, changing the potential gradient must change the amount of work that the pump does per cycle and thus might be expected to change either therate of pumping (i.e., magnitudes of the Na or K fluxes) or their sensitivity to external ions.