A slowly inactivating potassium current in native oocytes of Xenopus laevis.
A slowly inactivating potassium current in native oocytes of Xenopus laevis.
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非洲爪蟾天然卵母细胞中缓慢失活的钾电流。
DOI：
10.1098/rspb.1990.0005
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Ivorra,I
中科院分区：
文献类型：
--
作者：
Parker,I;Ivorra,I
记录了电压钳位非洲爪蟾卵母细胞对电压阶跃的膜电流反应。我们描述了从一个供体青蛙，这表明一个异常大的外向电流去极化后，获得的卵母细胞中获得的结果。对不同K+浓度溶液中尾电流反转电位的测量表明，尾电流主要由K+离子携带。这是强烈减少细胞外应用的四乙基铵，但不是由钡2+或4-氨基吡啶。去除周围的滤泡细胞并没有减少K+电流，表明它产生的卵母细胞膜适当。K+电导的激活首先在去极化至约-12 mV时检测到，对于电流的e倍变化，随着3 mV的极限电压灵敏度增加，并且在约+10 mV时半最大激活。去极化后，电流呈单指数时程上升，时间常数从-10 mV时的约400 ms缩短至+80 mV时的约15 ms。在延长的去极化过程中，电流失活的时间常数约为4 s，这并没有改变很大的电位。的K+电流是独立的Ca 2+，因为它不改变通过添加10 mM Mn 2+的浴介质，或通过细胞内注射EGTA。K+电流波动的噪声分析表明，电流由具有约20 ps的单位电导和约300 ms的平均开放寿命的通道携带（在室温和+10至+20 mV的电势下）。
Membrane currents were recorded in voltage-clamped oocytes ofXenopus laevisin response to voltage steps. We describe results obtained in oocytes obtained from one donor frog, which showed an unusually large outward current upon depolarization. Measurements of reversal potentials of tail currents in solutions of different K+concentration indicated that this current is carried largely by K+ions. It was strongly reduced by extracellular application of tetraethylammonium, though not by Ba2+or 4- aminopyridine. Removal of surrounding follicular cells did not reduce the K+current, indicating that it arises across the oocyte membrane proper. Activation of the K+conductance was first detected with depolarization to about –12 mV, increased with a limiting voltage sensitivity of 3 mV for an e-fold change in current, and was half-maximally activated at about +10 mV. The current rose following a single exponential timecourse after depolarization, with a time constant that shortened from about 400 ms at –10 mV to about 15 ms at +80 mV. During prolonged depolarization the current inactivated with a time constant of about 4 s, which did not alter greatly with potential. The K+current was independent of Ca2+, as it was not altered by addition of 10 mM Mn2+to the bathing medium, or by intracellular injection of EGTA. Noise analysis of K+current fluctuations indicated that the current is carried by channels with a unitary conductance of about 20 ps and a mean open lifetime of about 300 ms (at room temperature and potential of +10 to +20 mV).