Lipsius S L, Gibbons W R
Am J Physiol. 1982 Jul;243(1):H77-86. doi: 10.1152/ajpheart.1982.243.1.H77.
We examined relationships between isometric tension and membrane currents in sheep Purkinje fibers voltage clamped by the two-microelectrode method. Oscillatory restitution of contractility was accompanied by a small oscillation in membrane current and by an aftercontraction. The membrane current oscillation resembled the transient inward current (TI) others have reported in the presence of strophanthidin. Twitches produced by voltage clamp depolarizations did not correlate with net outward current in normal solution, but when the early outward current was blocked by 0.5 mM 4-aminopyridine, the residual outward current did correlate with twitches elicited by strong depolarizing clamps, particularly in solutions containing higher than normal calcium concentrations. The results illustrate important similarities and differences between membrane current behavior in sheep Purkinje fibers and behavior others have reported in calf fibers. Correlations between restitution, aftercontractions, and TI's, and between twitch tension and a component of outward current, may arise because of calcium regulation of membrane conductance, electrogenic Na-Ca exchange, or a combination of these and other mechanisms.
我们研究了采用双微电极电压钳制技术对绵羊浦肯野纤维进行电压钳制时，等长张力与膜电流之间的关系。收缩性的振荡恢复伴随着膜电流的小幅振荡和后收缩。膜电流振荡类似于其他人在毒毛花苷存在时报道的瞬时内向电流（TI）。在正常溶液中，电压钳去极化产生的抽搐与净外向电流无关，但当早期外向电流被0.5 mM 4-氨基吡啶阻断时，残余外向电流确实与强去极化钳制引发的抽搐相关，特别是在钙浓度高于正常的溶液中。结果表明，绵羊浦肯野纤维中的膜电流行为与其他人在小牛纤维中报道的行为之间存在重要的异同。恢复、后收缩和TI之间以及抽搐张力与外向电流成分之间的相关性，可能是由于钙对膜电导的调节、电致钠钙交换，或这些机制与其他机制的组合所致。
