Effects of vigorous isometric muscle contraction on titin stiffness-related contractile properties in rat fast-twitch muscles
Effects of vigorous isometric muscle contraction on titin stiffness-related contractile properties in rat fast-twitch muscles
复制标题
DOI：
10.1152/ajpregu.00189.2021
复制
发表时间：
2021-12-01
影响因子：
2.8
通讯作者：
Wada, Masanobu
中科院分区：
文献类型：
--
作者：
Shi, Jiayu;Watanabe, Daiki;Wada, Masanobu
本研究旨在研究大鼠快速收缩骨骼肌急性剧烈等距收缩对肌体刚度相关收缩特性的影响。原位电刺激完整腓肠肌，直到力减少到初始力的50%。在刺激停止后，立即解剖肌肉的浅表区域，并进行生化和皮肤纤维分析。刺激导致titin基被动力降低。碎片化titin的数量在刺激下没有变化。蛋白激酶C α处理增加了受刺激纤维的被动力到静息水平。在肌节长度（SL）为2.4 μ m时，刺激对最大Ca2+激活力（max Ca2+ force）没有影响，而在2.6 μ m SL时，刺激降低了肌纤维(my)-Ca2+敏感性。将SL拉伸到3.0 μ m时，休息和刺激纤维的最大Ca2+力和my-Ca2+敏感性都增加了。对于最大Ca2+力，刺激纤维的增加幅度小于休息纤维，而对于myCa（2+）敏感性，刺激纤维的增加幅度高于休息纤维。这些结果表明，剧烈的等长收缩减少了基于titin的被动力，可能是因为蛋白激酶C α磷酸化的减少，而titin刚度的降低可能至少部分地导致肌肉疲劳。
This study was conducted to examine the effects of an acute bout of vigorous isometric contractions on titin stiffness-related contractile properties in rat fast-twitch skeletal muscles. Intact gastrocnemius muscles were electrically stimulated in situ until the force was reduced to similar to 50% of the initial force. Immediately after cessation of the stimulation, the superficial regions of the muscles were dissected and subjected to biochemical and skinned fiber analyses. The stimulation resulted in a decrease in the titin-based passive force. The amounts of fragmented titin were unchanged by the stimulation. Protein kinase C alpha-treatment increased the passive force in stimulated fibers to resting levels. The stimulation had no effect on the maximum Ca2+-activated force (max Ca2+ force) at a sarcomere length (SL) of 2.4 mu m and decreased myofibrillar (my)-Ca2+ sensitivity at 2.6-mu m SL. Stretching the SL to 3.0 mu m led to the augmentation of the max Ca2+ force and my-Ca2+ sensitivity in both rested and stimulated fibers. For the max Ca2+ force, the extent of the increase was smaller in stimulated than in rested fibers, whereas for myCa(2+) sensitivity, it was higher in stimulated than in rested fibers. These results suggest that vigorous isometric contractions decrease the titin-based passive force, possibly because of a reduction in phosphorylation by protein kinase C alpha, and that the decreased titin stiffness may contribute, at least in part, to muscle fatigue.