Phase transition in force during ramp stretches of skeletal muscle
Phase transition in force during ramp stretches of skeletal muscle
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DOI：
10.1016/s0006-3495(98)77738-0
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发表时间：
1998-12-01
影响因子：
3.4
通讯作者：
Lehman, SL
中科院分区：
文献类型：
--
作者：
Getz, EB;Cooke, R;Lehman, SL
在肌节长度控制下，以恒定速度（0.1-3.0长度/s）拉伸活性甘油化兔腰肌纤维。正如以前的研究者所观察到的，力的上升分为两个阶段：在一小段时间内（第一阶段），力的上升很快，在剩下的时间里（第二阶段），力的上升较慢，幅度较小。两相之间的转变发生在7.7 +/- 0.1 nm/半肌节的临界拉伸（L-C）处，该临界拉伸与速度无关。临界拉伸力（P-C）随速度增加至1长度/s，然后恒定在3.26 +/- 0.06倍等长力。在拉伸过程中，对小步拉伸的力响应的衰减比等长纤维快得多。添加3 mM钒酸盐使等长收缩张力降低至对照等长收缩张力（P-o）的0.08 +/- 0.01倍，但仅使P-C降低至P-o的0.82 +/- 0.06倍，表明在拉伸期间，预动力冲程状态有助于力的升高。这些数据可以用一个模型来解释，在这个模型中，肌动蛋白连接的横桥在prepowerstroke状态下被拉伸到高力区域，并且当拉伸超过该区域时非常迅速地分离。前动力冲程状态作为一个机械整流器，在拉伸过程中产生大的力，但在缩短过程中产生小的力。
Active glycerinated rabbit psoas fibers were stretched at constant velocity (0.1-3.0 lengths/s) under sarcomere length control. As observed by previous investigators, force rose in two phases: an initial rapid increase over a small stretch (phase I), and a slower, more modest rise over the remainder of the stretch (phase II). The transition between the two phases occurred at a critical stretch (L-C) of 7.7 +/- 0.1 nm/half-sarcomere that is independent of velocity. The force at critical stretch (P-C) increased with velocity up to 1 length/s, then was constant at 3.26 +/- 0.06 times isometric force. The decay of the force response to a small step stretch was much faster during stretch than in isometric fibers. The addition of 3 mM vanadate reduced isometric tension to 0.08 +/- 0.01 times control isometric tension (P-o), but only reduced P-C to 0.82 +/- 0.06 times P-o, demonstrating that prepowerstroke states contribute to force rise during stretch. The data can be explained by a model in which actin-attached cross-bridges in a prepowerstroke state are stretched into regions of high force and detach very rapidly when stretched beyond this region. The prepowerstroke state acts as a mechanical rectifier, producing large forces during stretch but small forces during shortening.