An endogenous inactivating inward-rectifying potassium current in oocytes of Xenopus laevis
An endogenous inactivating inward-rectifying potassium current in oocytes of Xenopus laevis
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DOI：
10.1007/s004240050203
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发表时间：
1996-09-01
影响因子：
4.5
通讯作者：
Schwarz, JR
中科院分区：
文献类型：
--
作者：
Bauer, CK;Falk, T;Schwarz, JR
描述了内源性内向整流 K+ 电流，该电流存在于一些非洲爪蟾供体的天然卵母细胞中。实验使用来自两个不同供应商的供体青蛙的去卵母细胞进行。在来自同一来源的动物的所有卵母细胞中，在高 K+ 浓度的外部溶液中，通过 -20 mV 的保持电位的负脉冲可以引发内向整流 K+ 电流。增加外部 K+ 浓度会增加该电流的幅度，并将反转电位转向更正的电位。在 118 mM KCl 中，内向整流 K+ 电流在 -20 至 -80 mV 之间部分失活，在更负的膜电位下完全失活； 50% 稳态失活发生在 -50 mV 附近。内向整流电流失活的时间过程可以很好地用两个指数拟合。慢时间常数的值约为 500 ms，并且与电压无关。相反，快速时间常数和达到峰值内向电流的时间随着膜电位负值的增加而减少。 Ba2+、Cs+、奎宁（均为 5 mM）和 50 mM 四乙铵部分阻断内向整流 K+ 电流，而 10 mM 4-氨基吡啶则没有阻断作用。氧化剂氯胺-T 阻断了内向整流 K+ 电流，但没有减慢其失活速度。
An endogenous inward-rectifying K+ current is described, which is present in native oocytes of some Xenopus laevis donors. Experiments were performed using defolliculated oocytes from donor frogs obtained from two different suppliers. In all oocytes from animals from one source, an inward-rectifying K+ current could be elicited with negative pulses from a holding potential of -20 mV in external solutions with a high K+ concentration. Increasing external K+ concentrations increased the amplitude of this current and shifted the reversal potential towards more positive potentials. In 118 mM KCl, the inward-rectifying K+ current partially inactivated between -20 and -80 mV and completely inactivated at more negative membrane potentials; 50% steady-state inactivation occurred near -50 mV. The time course of inactivation of the inward-rectifying current could be well fitted with two exponentials. The slow time constant had values of about 500 ms and was voltage independent. In contrast, the fast time constant and the time to reach the peak inward current decreased with more negative membrane potentials. Ba2+, Cs+, quinine (all 5 mM) and 50 mM tetraethylammonium partially blocked the inward-rectifying K+ current, whereas 10 mM 4-aminopyridine was without blocking effect. The oxidant chloramine-T blocked the inward-rectifying K+ current without slowing its inactivation.