Dominguez G, Fozzard H A
Am J Physiol. 1979 Sep;237(3):C119-24. doi: 10.1152/ajpcell.1979.237.3.C119.
Cardiac Purkinje fibers were studied before and after stretch to 30% and 50% in excess of their slack length, and membrane properties and conduction velocity were measured in relation to the stretch. Conduction velocity increased by 26% with 50% stretch. The resting potentials averaged -77 mV and did not change with stretch. In addition, the action potential height, maximal upstroke velocity, duration, and time constant of the foot did not change. These results suggested that the increase in conduction velocity was not due to a change in membrane excitability. Two geometric models of stretch, called unfolding and uncoiling, were considered. Cable analyses were performed to distinguish between these models. The effects were mixed, with about 2/3 of the length change resulting from unfolding and 1/3 from uncoiling. These results support the concept of redundancy of the surface membrane by folding. The changes are likely to be of importance in activation of the heart by the His-Purkinje system, especially in cardiac dilatation due to disease.
对心脏浦肯野纤维在拉伸至超过其松弛长度30%和50%之前和之后进行了研究，并测量了与拉伸相关的膜特性和传导速度。在50%拉伸时，传导速度增加了26%。静息电位平均为-77mV，且不随拉伸而变化。此外，动作电位高度、最大上升速度、持续时间和足部时间常数均未改变。这些结果表明，传导速度的增加并非由于膜兴奋性的改变。考虑了两种拉伸的几何模型，分别称为展开和解盘绕。进行电缆分析以区分这些模型。结果是混合的，约2/3的长度变化是由展开引起的，1/3是由解盘绕引起的。这些结果支持了通过折叠使表面膜冗余的概念。这些变化可能对希氏-浦肯野系统激活心脏很重要，尤其是在因病导致心脏扩张时。
