Voltage-clamp studies on the canine Purkinje strand.
Voltage-clamp studies on the canine Purkinje strand.
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对犬浦肯野链的电压钳研究。
DOI：
10.1098/rspb.1983.0007
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Kline,RP
中科院分区：
文献类型：
--
作者：
Cohen,IS;Falk,RT;Kline,RP
为应用双微电极电压钳技术，从成年杂种犬左、右室切取浦肯野线束，切成小于2.0 mm的长度。解剖后，相当一部分准备工作完全恢复，静息电位大于-80 mV，上搏速度大于290V S-1。对小电流脉冲电压响应的分析表明，短蒲肯野绞线可视为一维简单的有限长一维电缆，两端具有无限大的电阻。平均长度常数为2.5 mm。在保持相对较长的长度恒定的情况下，沿链插入第三个微电极显示了电压钳的高度纵向均匀度。对容量瞬变的分析给出了归一化为圆柱形表面积的总容量为11.5Fcm2的估计。μF cm-2。电容瞬变的最终衰减是一个平均时间常数为1毫秒的单一指数。在电导率正常的溶液和电导率降低(13%)的溶液中，电容瞬变最终衰减的第二个较慢的分量都不存在。这表明胞外串联阻力可能相对较小。通过测量耗竭电流与瞬时电流的比值来估计K+耗竭电流的大小。这一比率平均为10%。这两个结果与所附文件中描述的形态计量学数据一致，表明犬类制剂比有蹄类制剂具有更宽的细胞外裂隙。证明了包括起搏器电流在内的全部内向和外向电流的存在。宽裂隙的存在不会影响起搏器电流反转的电位(在4 mM[K+]Tyrode溶液中约为-107 mV)，因为起搏器电流在犬浦肯野制剂中的反转电位与在有蹄类动物中大致相同。
Purkinje strands were excised from the left and right ventricles of adult mongrel dogs and cut to lengths of less than 2.0 mm in order to apply the two-microelectrodes voltage-clamp technique. A sizeable fraction of these preparations fully recover following dissection, with resting potentials more negative than – 80 mV and upstroke velocities faster than 290 V s-1. Analysis of the voltage response to small current pulses shows that the short Purkinje strands can be treated as simple finite one-dimensional cables with ends of infinite resistance. The average length constant is 2.5 mm. In keeping with the relatively long length constant, insertion of a third microelectrode along the strand demonstrates a high degree of longitudinal homogeneity of the voltage clamp. Analysis of the capacity transient gives an estimate of the total capacity, normalized to cylindrical surface area, of 11.5 μF cm-2. The final decay of the capacity transient is a single exponential with an average time constant of 1 ms. A second slower component to the final decay of the capacity transient is absent in solutions of normal conductivity as well as in solutions of reduced (13%) conductivity. This suggests that the extracellular series resistance may be relatively small. The magnitude of the K+depletion current was estimated by measuring the ratio of depletion current to instantaneous current. This ratio averaged 10%. These two results are consistent with the morphometric data described in the accompanying paper, which show that the canine preparation has wider extracellular clefts than the ungulate preparation. The existence of the full complement of inward and outward currents, including the pacemaker current, is demonstrated. The presence of wide clefts does not affect the potential at which the pacemaker current reverses (about –107 mV in 4 mm [K+] Tyrode solution), since the pacemaker current reverses at approximately the same potential in the canine Purkinje preparation as it does in the ungulate.