SODIUM-CHANNELS INDUCED BY DEPOLARIZATION OF THE XENOPUS-LAEVIS OOCYTE
SODIUM-CHANNELS INDUCED BY DEPOLARIZATION OF THE XENOPUS-LAEVIS OOCYTE
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DOI：
10.1073/pnas.79.10.3188
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发表时间：
1982-01-01
期刊：
影响因子：
--
通讯作者：
MARCHER, K
中科院分区：
文献类型：
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作者：
BAUD, C;KADO, RT;MARCHER, K
可以使电门控Na+通道出现在X的膜中。通过简单去极化将卵母细胞分离。该膜通常被动地响应于具有静息电位的施加的跨膜电流。-60 mV，但当其保持去极化至大于+30 mV时，可以获得高达+80 mV的持久再生去极化;这些去极化可持续长达20 min。该电位是由于诱导了一个Na+依赖性通道，该通道是电门控打开和关闭的。其打开阈值为. apprx。-20 mV，并且相对于Cs+和胆碱+，它对Na+具有选择性，但被相对少量的Li+阻断。当在ENa [Na平衡电位]（+70至+90 mV）下施加长电压钳步骤至正电位时，观察到内向电流持续数分钟，这意味着该通道不具有失活机制。内向Na+电流被0.50 mM河豚毒素阻断。当细胞膜保持在静息电位或接近静息电位时，兴奋性会随着时间的推移而消失，但可以通过再次去极化细胞膜使其重新出现。
An electrically gated Na+ channel can be made to appear in the membrane of the X. laevis oocyte by simple depolarization. This membrane normally responds passively to imposed transmembrane currents with resting potentials .apprx. -60 mV, but when it is held depolarized to more than .apprx. +30 mV it becomes possible to obtain long-lasting regenerative depolarizations up to +80 mV; these depolarizations can last as long as 20 min. This potential is due to an induction of a Na+-dependent channel that is electrically gated open and closed. Its threshold for opening is .apprx. -20 mV and it is selective for Na+ over Cs+ and choline+ but is blocked by relatively small quantities of Li+. When a long voltage clamp step to a positive potential under ENa [Na equilibrium potential] (+70 to +90 mV) is applied, an inward current is observed for many minutes, implying that this channel does not have an inactivation mechanism. The inward Na+ current is blocked by 0.50 mM tetrodotoxin. When the membrane is held at or near resting potential, the excitability will disappear with time, but it can be made to reappear by again depolarizing the membrane.