Expression and characterization of a canine hippocampal inwardly rectifying K+ current in Xenopus oocytes.
Expression and characterization of a canine hippocampal inwardly rectifying K+ current in Xenopus oocytes.
复制标题
爪蟾卵母细胞中犬海马内向整流 K 电流的表达和特征。
DOI：
10.1113/jphysiol.1992.sp019375
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Cohen,IS
中科院分区：
文献类型：
--
作者：
Cui,J;Mandel,G;DiFrancesco,D;Kline,RP;Pennefather,P;Datyner,NB;Haspel,HC;Cohen,IS
1.用双微电极电压钳技术研究了注入犬海马poly（A）+RNA的非洲爪蟾卵母细胞表达的内向整流钾电流。2.爪蟾卵母细胞注射犬海马poly（A）+RNA表达电流激活超极化。该电流包含瞬时分量和时间依赖分量。这两种成分都是内向整流的，可被细胞外Cs+或Ba~（2+）阻断。3.表达电流主要由K+携带。在不同[K +] o下测得的反转电位可用能斯特方程拟合，[K +] o每变化10倍，斜率为-50.7。细胞外Cl-和Na+对电流的贡献最小。4.表达电流的激活取决于电压和[K +] o。当[K +] o改变时，激活曲线沿平行于EK的电压轴沿着移动。5.表达电流的激活时间常数也依赖于电压和[K +] o。时间常数的电压依赖性呈钟形，峰值位于比EK负30 - 50 mV的电位处。当EK改变时，时间常数的电压依赖性沿电压轴发生沿着移动。6.在10 - 31%线性蔗糖梯度中分离从犬海马提取的poly（A）+RNA。表达内向整流电流所需的mRNA的大小估计为约4kb。7.总之，所表达的电流是内向整流钾电流。犬海马mRNA应该是表达克隆内向整流通道的极好来源。
1. An inwardly rectifying potassium current expressed in Xenopus laevis oocytes injected with canine hippocampal poly(A)+ RNA was investigated with the two‐microelectrode voltage clamp technique. 2. Xenopus oocytes injected with canine hippocampal poly(A)+ RNA expressed a current activated by hyperpolarization. This current contained an instantaneous and a time‐dependent component. Both components were inwardly rectifying and could be blocked by extracellular Cs+ or Ba2+. 3. The expressed current was carried mainly by K+. Its reversal potential measured in different [K+]os could be fitted by the Nernst equation with a slope of ‐50.7 per tenfold change in [K+]o. Extracellular Cl‐ and Na+ made minimal contributions to the current. 4. The activation of the expressed current depended on both voltage and [K+]o. Activation started near EK and the activation curve shifted along the voltage axis in parallel with EK when [K+]o was altered. 5. The activation time constants of the expressed current also depended on both voltage and [K+]o. The voltage dependence of the time constants was bell‐shaped and the peak value was at a potential 30‐50 mV more negative than EK. The voltage dependence of the time constants shifted along the voltage axis when EK was changed. 6. The poly(A)+ RNA extracted from canine hippocampus was fractionated in a 10‐31% linear sucrose gradient. The size of the mRNA required to express the inwardly rectifying current was estimated to be around 4 kb. 7. In conclusion, the expressed current is an inwardly rectifying potassium current. The canine hippocampal mRNA should be an excellent source for expression‐cloning of the inward rectifier channel.