Rosen M R, Legato M J, Weiss R M
Am J Physiol. 1981 Apr;240(4):H546-54. doi: 10.1152/ajpheart.1981.240.4.H546.
We studied the age-related changes that occur in conduction in Purkinje fiber bundles (PF) from adult and 8-wk-old dogs. As PF are stretched, conduction velocity increases to a maximum when bundle length is approximately 1.5 times control. Conduction velocity in adult PF was significantly faster than that in 8-wk PF at all bundle lengths, the maximum being 2.32 +/- 0.45 m/s (mean +/- SD) in adult and 1.56 +/- 0.59 m/s in 8-wk-old dogs. At greater than 1.5 times control length, conduction velocity decreased, as did resting potential, action potential amplitude, and upstroke velocity. At 1.5 times control length, the ratio of PF to collagen in the bundles increased, and structural changes consistent with both unbuckling and unfolding of the cell membranes were seen. At greater degrees of stretch, cleft size diminished, and intracellular edema was noted. In sum, structural changes in cardiac PF can explain the changes in conduction velocity that occur with stretch. At all degrees of stretch, however, velocity is faster in PF from adult than from young dogs.
我们研究了成年犬和8周龄犬浦肯野纤维束（PF）中与年龄相关的传导变化。随着PF被拉伸，当束长度约为对照的1.5倍时，传导速度增加到最大值。在所有束长度下，成年PF的传导速度均显著快于8周龄PF，成年犬的最大值为2.32±0.45 m/s（平均值±标准差），8周龄犬为1.56±0.59 m/s。当大于对照长度的1.5倍时，传导速度下降，静息电位、动作电位幅度和上升速度也下降。在对照长度的1.5倍时，束中PF与胶原蛋白的比例增加，并且观察到与细胞膜解扣和展开一致的结构变化。在更大程度的拉伸下，裂隙尺寸减小，并注意到细胞内水肿。总之，心脏PF的结构变化可以解释拉伸时发生的传导速度变化。然而，在所有拉伸程度下，成年犬PF的速度都比幼犬快。
