Sodium current in single rat heart muscle cells.
Sodium current in single rat heart muscle cells.
复制标题
单只大鼠心肌细胞中的钠电流。
DOI：
10.1113/jphysiol.1981.sp013879
复制
发表时间：
1981
期刊：
影响因子：
--
通讯作者：
Powell,T
中科院分区：
文献类型：
--
作者：
Brown,AM;Lee,KS;Powell,T
1.应用双吸移管电压钳技术研究了大鼠心室肌细胞快速内向钠电流（INa）。所有实验均在20 - 22 ℃下进行。2.通过单次去极化电压阶跃从-80 mV的保持电位VH诱发的INa阈值在-70 mV至-60 mV之间，最大值在-30 mV至-20 mV。假设平均细胞表面积为8000平方微米，含145 mM Na的Krebs-Ringer溶液中的峰值电流约为0.9 - 1.8 mA cm-2。3.通过外部Na在1.45 - 145 mM范围内的能斯特方程预测INa的逆转电位，其中16 mM-Na溶液灌注细胞内部。4.瞬时I-V曲线在-100至+ 10 mV的电位下呈线性。在145 mM-Na溶液中，最大Na电导率（-gNa）计算为25 mS cm-2，gNa在-10 mV的正电位下保持恒定。5. INa在-55 mV下以0.7 msec的时间常数激活，在去极化为正至+ 10 mV时降低至100微秒。6.需要两个时间常数（tau h 1，tau h 2）来描述在维持去极化过程中的INa失活，tau h 2是tau h 1的三到四倍。tau h1在-50 mV时约为2 msec，在-10 mV时降至0.9 msec。7. INa从失活中恢复的时间过程也显示出两个时间常数（tau r1，tau r2），较长的tau r2在-60至-80 mV的电位范围内具有约100 msec的最大值。8.分离的大鼠心肌细胞中的INa对河豚毒素的敏感性较低，需要30 μ M的浓度才能完全阻断。
1. Rapid inward Na current (INa) was studied in isolated cells from rat ventricular myocardium by a double‐suction‐pipette voltage clamp technique. All experiments were carried out at 20‐22 degrees C. 2. INa elicited by single depolarizing voltage steps from a holding potential, VH, of ‐80 mV had a threshold between ‐70 and ‐60 mV and was maximal at ‐30 to ‐20 mV. Peak currents in Krebs‐Ringer solution containing 145 mM Na were of the order 0.9‐1.8 mA cm‐2, assuming an average cell surface area of 8000 square micrometers. 3. The reversal potential for INa was predicted by the Nernst equation for external Na in the range 1.45‐145 mM with 16 mM‐Na solution perfusing the interior of the cell. 4. Instantaneous I‐V plots were linear for potentials of ‐100 to + 10 mV. Maximum Na conductance (‐gNa) was calculated to be 25 mS cm‐2 in 145 mM‐Na solutions and gNa was constant for potentials positive to ‐10 mV. 5. INa activated with a time constant of 0.7 msec at ‐55 mV, decreasing to 100 microsec on depolarizations positive to + 10 mV. 6. Two time constants (tau h1, tau h2) were required to describe INa inactivation during a maintained depolarization, with tau h2 three to four times as long as tau h1. tau h1 was about 2 msec at ‐50 mV, decreasing to 0.9 msec at ‐10 mV. 7. The time course for recovery of INa from inactivation also exhibited two time constants (tau r1, tau r2), with the longer tau r2 having a maximum value of the order 100 msec in the potential range ‐60 to ‐80 mV. 8. INa in isolated rat cardiac cells has a low sensitivity to tetrodotoxin, requiring a concentration of 30 micrometers for complete blockade.