Levis R A, Mathias R T, Eisenberg R S
Biophys J. 1983 Nov;44(2):225-48. doi: 10.1016/S0006-3495(83)84295-7.
The impedence of sheep Purkinje strands, measured to 3-5 kHz, is interpreted with circuit models based on morphology. The strand is described as a one-dimensional electrical cable. Clefts between myocytes of the strand allow radial current to flow in parallel with current across the outer membrane. A lumped model of the clefts, in which all the cleft membrane is in series with 100 omega-cm2, fits only below 20 Hz. Two distributed models, pie and disk, fit at all frequencies with somewhat different (31%) luminal resistivities, but with similar membrane parameters. Series resistance representing the endothelial sheath is small. Simulations of voltage clamp experiments include measured linear parameters and nonlinear membrane channels, as well as radial variation of cleft concentration, membrane flux, voltage, and current. Cleft potential is drastically nonuniform when sodium current flows. Cleft potential is reasonably uniform when calcium and potassium currents flow, but the calcium and potassium concentrations change markedly, enough to turn off the calcium current, even if the calcium channel did not inactivate. We conclude that physiological current flows produce significant nonuniformities in electrochemical potentials in the clefts of this cardiac preparation.
测量绵羊浦肯野纤维束在3至5千赫兹频率下的阻抗，并根据其形态用电路模型进行解释。该纤维束被描述为一维电缆。纤维束肌细胞之间的缝隙允许径向电流与跨外膜的电流平行流动。缝隙的集总模型（其中所有缝隙膜与100欧厘米²串联）仅在20赫兹以下适用。两种分布式模型，即饼状模型和盘状模型，在所有频率下都适用，管腔电阻率略有不同（31%），但膜参数相似。代表内皮鞘的串联电阻很小。电压钳实验的模拟包括测量的线性参数和非线性膜通道，以及缝隙浓度、膜通量、电压和电流的径向变化。当钠电流流动时，缝隙电位极不均匀。当钙电流和钾电流流动时，缝隙电位相当均匀，但钙和钾浓度变化显著，足以使钙电流关闭，即使钙通道没有失活。我们得出结论，生理电流流动会在这种心脏标本的缝隙中产生显著的电化学势不均匀性。
