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Effects of exercise training on the ultrastructural alterations of membrane systems involved in excitation-contraction coupling during contraction in skeletal muscle.

运动训练对骨骼肌收缩过程中参与兴奋-收缩耦合的膜系统超微结构改变的影响。

基本信息

批准号：
10480009
负责人：
TAKEKURA Hiroaki
金额：
$ 2.43万
依托单位：
National Institute of Fitness and Sports in Kanoya
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

Excitation-contraction (E-C) coupling is the series of steps that leads from the electrical event at the surface if the muscle fiber (excitation) to contraction of the muscle fibers. Two major membrane components directly concerned with the E-C coupling process : transverse (T) tubules and sarcoplasmic reticulum (SR). T tubules are invaginations of the surface membrane which penetrate into the muscle fibers and form transverse networks at precisely repeated intervals. T tubules transmit the electrical signal to the center of the muscle fiber. The SR is an internal membrane system equivalent to the endoplasmic reticulum of other cells, which is located in the space between the myofibrils. The SR sequesters calcium (Ca^<2+>) from the myofibrils. T tubules and SR form specialized junctions, the triads. Physiological evidence suggests the possibility that the E-C coupling failure with eccentric contraction-induced muscle injury is due to structural and morphological damage to membrane systems directly associated with the E-C coupling processes within skeletal muscle fibres. We observed the ultrastructural features of the membrane systems of rat fast-twitch (FT) and slow-twitch (ST) muscle fibres involved in E-C coupling following level and downhill running exercise. There were four obvious ultrastructural changes in the arrangement of the T tubules and the disposition of triads after the downhill running exercise : (1) an increase in the numbers of longitudinal segments of the T tubule network, (2) changes in the direction and disposition of triads, (3) the appearance of caveolar clusters, and (4) the appearance of pentads and heptads. These observations also support the idea that eccentric-exercise-induced E-C coupling failure is due to physical and chemical disruptions of the membrane systems involved in the E-C coupling process in skeletal muscle.

兴奋-收缩（E-C）耦合是从肌纤维表面的电事件（兴奋）到肌纤维收缩的一系列步骤。两个主要的膜组件直接涉及E-C耦合过程：横（T）管和肌浆网（SR）。T小管是表面膜的内陷，其渗透到肌纤维中并以精确重复的间隔形成横向网络。T小管将电信号传输到肌纤维的中心。SR是一个相当于其他细胞内质网的内膜系统，位于肌原纤维之间的空间。SR从肌原纤维中螯合钙（Ca ^2+）。T小管和SR形成专门的连接，三联体。生理学证据表明，偏心收缩引起的肌肉损伤的E-C耦合失败的可能性是由于骨骼肌纤维内与E-C耦合过程直接相关的膜系统的结构和形态学损伤。观察了大鼠在水平和下坡跑运动后参与电-电偶联的快缩肌（FT）和慢缩肌（ST）纤维膜系统的超微结构特征。下坡跑运动后T小管的排列和三联体的分布有四种明显的超微结构变化：（1）T小管网络的纵节数增加;（2）三联体的方向和分布发生变化;（3）出现小窝簇;（4）出现五联体和七联体。这些观察结果也支持离心运动引起的E-C耦合失败是由于骨骼肌中参与E-C耦合过程的膜系统的物理和化学破坏。