Tidball J G, Daniel T L
Am J Physiol. 1986 Jan;250(1 Pt 2):R56-64. doi: 10.1152/ajpregu.1986.250.1.R56.
The capability of heavy meromyosin (HMM) to store energy in reversible deformations has been investigated previously; yet, whether HMM is the site of most elastic energy storage in skeletal muscle cells has not been established. We conducted dynamic loading tests on single rigored muscle cells over the physiological range of sarcomere lengths. These tests enabled us to calculate the energy stored in reversible deformations or dissipated in the cell during each cycle of oscillation. Our findings show that these cells are capable of storing approximately 0.5 J . kg-1 of elastic energy during the last 50 ms of passive extension in vivo by agonists and before their own active contraction. Possible sites of this energy storage are HMM subunit 2, the proximal portion of HMM subunit 1, and parallel structures. However, energy storage increases monotonically as myofilament overlap decreases in the physiological range. This negative correlation suggests that HMM subunits are not the primary sites of elastic energy storage. Our electron-microscopic observations show that collagen fibrils at the cell's surface become oriented parallel to the cell's long axis over the range of sarcomere lengths where energy storage increases. This provides a mechanism for the observed increases in elastic energy storage.
此前已对重酶解肌球蛋白（HMM）在可逆变形中储存能量的能力进行了研究；然而，HMM是否是骨骼肌细胞中弹性储能的主要部位尚未确定。我们在肌节长度的生理范围内对单个僵直肌肉细胞进行了动态加载测试。这些测试使我们能够计算在每个振荡周期中细胞在可逆变形中储存或耗散的能量。我们的研究结果表明，在体内由激动剂进行被动伸展的最后50毫秒且细胞自身主动收缩之前，这些细胞能够储存约0.5焦耳·千克-1的弹性能量。这种能量储存的可能部位是HMM亚基2、HMM亚基1的近端部分和平行结构。然而，在生理范围内，随着肌丝重叠减少，能量储存单调增加。这种负相关表明HMM亚基不是弹性储能的主要部位。我们的电子显微镜观察表明，在能量储存增加的肌节长度范围内，细胞表面的胶原纤维会与细胞长轴平行排列。这为观察到的弹性能量储存增加提供了一种机制。
