Duchatelle-Gourdon I, Hartzell H C
Department of Anatomy and Cell Biology, Emory University School of Medicine, Atlanta, GA 30322.
Biophys J. 1990 Apr;57(4):903-9. doi: 10.1016/S0006-3495(90)82610-2.
The patch-clamp technique with two pipettes was used to record single delayed K+ channels (cell-attached electrode) and to control the potential and the composition of the intracellular compartment (whole-cell electrode). With 30 microM cAMP in the cell and physiological potassium concentrations inside and outside the patch, a channel carrying an outward current was characterized. Its open probability was very low and the channel was recorded in only 5% of patches under control conditions. Increasing intracellular cAMP increased the probability of finding a channel in a patch 10-fold. The channel had the characteristics expected of a delayed rectifier channel. The time-course of its ensemble average resembled the whole-cell current in the same cell. The current-voltage relationship exhibited inward rectification, with a slope conductance of 20 pS in the linear portion and a reversal potential close to EK. Both the open- and the closed-time distributions were described by the sum of two exponentials, suggesting a complicated gating scheme involving two closed states and two open states. The beta-adrenergic stimulation did not change the conductance of the channel, but increased its probability of opening.
采用双电极膜片钳技术记录单个延迟钾通道（细胞贴附式电极），并控制细胞内区室的电位和成分（全细胞膜片电极）。在细胞内加入30微摩尔/升的环磷酸腺苷（cAMP），且膜片内外钾离子浓度处于生理水平时，对一个携带外向电流的通道进行了表征。其开放概率非常低，在对照条件下，仅在5%的膜片中记录到该通道。增加细胞内cAMP可使在膜片中发现该通道的概率提高10倍。该通道具有延迟整流通道预期的特征。其总体平均值的时间进程与同一细胞中的全细胞电流相似。电流-电压关系呈现内向整流，线性部分的斜率电导为20皮西门子，反转电位接近钾平衡电位（EK）。开放时间和关闭时间分布均由两个指数函数之和描述，提示存在一种涉及两个关闭状态和两个开放状态的复杂门控机制。β-肾上腺素能刺激并未改变该通道的电导，但增加了其开放概率。
