Abstract：
The disuse of skeletal limb muscles occurs in a variety of conditions, yet our comprehension of the molecular mechanisms involved in adaptation to disuse remains incomplete. We studied the mechanical characteristics of actin-myosin interaction using an in vitro motility assay and isoform composition of myosin heavy and light chains by dint of SDS-PAGE in soleus muscle of both control and hindlimb-unloaded rats. 14 days of hindlimb unloading led to the increased maximum sliding velocity of actin, reconstituted, and native thin filaments over rat soleus muscle myosin by 24 %, 19 %, and 20 %, respectively. The calcium sensitivity of the \"pCa-velocity\" relationship decreased. There was a 26 % increase in fast myosin heavy chain IIa (MHC IIa), a 22 % increase in fast myosin light chain 2 (MLC 2f), and a 13 % increase in fast MLC 1f content. The content of MLC 1s/v, typical for slow skeletal muscles and cardiac ventricles did not change. At the same time, MLC 1s, typical only for slow skeletal muscles, disappeared. The maximum velocity of soleus muscle native thin filaments was 24 % higher compared to control ones sliding over the same rabbit myosin. Therefore, both myosin and native thin filament kinetics could influence the mechanical characteristics of the soleus muscle. Additionally, the MLC 1s and MLC 1s/v ratio may contribute to the mechanical characteristics of slow skeletal muscle, along with MHC, MLC 2, and MLC 1 slow/fast isoforms ratio.
摘要：
骨骼肌的废弃发生在各种情况下，然而，我们对适应废弃的分子机制的理解仍然不完整。我们使用体外运动性测定法研究了肌动蛋白-肌球蛋白相互作用的机械特性，并通过SDS-PAGE在对照和后肢无负荷大鼠的比目鱼肌中研究了肌球蛋白重链和轻链的同工型组成。14天的后肢卸载导致肌动蛋白的最大滑动速度增加，重组，和大鼠比目鱼肌肌球蛋白24％的天然细丝，19%,20%,分别。“pCa-速度”关系的钙敏感性降低。快速肌球蛋白重链IIa（MHCIIa）增加了26％，快速肌球蛋白轻链2（MLC2f）增加22％，MLC1f含量快速增加13%。MLC1s/v的含量，典型的缓慢骨骼肌和心室没有改变。同时,MLC1s,仅适用于慢速骨骼肌，消失了。比目鱼肌天然细丝的最大速度比在相同的兔肌球蛋白上滑动的对照组高24％。因此,肌球蛋白和天然细丝动力学都会影响比目鱼肌的力学特性。此外,MLC1s和MLC1s/v比可能有助于慢速骨骼肌的机械特性，连同MHC,MLC2和MLC1慢/快同种型比。
