Microgravity-induced transformations of myosin isoforms and contractile properties of skeletal muscle
Microgravity-induced transformations of myosin isoforms and contractile properties of skeletal muscle
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DOI：
10.1152/jappl.1996.81.1.123
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发表时间：
1996-07-01
影响因子：
3.3
通讯作者：
Baldwin, KM
中科院分区：
文献类型：
--
作者：
Caiozzo, VJ;Haddad, F;Baldwin, KM
本研究观察了微重力(14天)对1)反重力骨骼肌--比目鱼肌(SOL)的收缩特性的影响，以及(2)SOL、股中间肌(CVI)、足底(PLAN)和胫骨前肌(TA)肌的肌球蛋白重链(MHC)蛋白和mRNA异构体含量的变化。飞行SOL肌力-速度关系的最大等长张力显著降低(-37%)，最大缩短速度相应增加(+20%)。此外，飞行SOL肌肉的力-频率关系被移动到地面控制组的右侧。微重力对SOL肌中肌纤维组成的影响最大，慢肌纤维减少，杂交肌纤维相应增加。Sol和VI型肌肉中MHC亚型的绝对含量变化最大，慢型I型和快型IIX型MHC蛋白亚型含量分别显著降低和升高。与蛋白质数据一致，飞行SOL和VI肌肉在快型IIX MHC mRNA亚型中都显示出显著的升高。然而，相比之下，飞行计划组和TA组的快型IIB MHC mRNA异构体含量显著增加，而在蛋白质水平上没有相应的变化。这项研究的结果表明，即使是短时间的航天飞行，也会使反重力骨骼肌的收缩特性发生重要变化。这些变化是通过MHC表型的改变和肌肉质量的减少来调节的。在某些情况下，MHC信使核糖核酸异构体含量的改变似乎与发生在蛋白质水平上的改变无关。MRNA和蛋白质表达之间的这种明显的解偶联表明，必须在转录、翻译和翻译后水平上更好地理解微重力的影响。
This study examined the effects of microgravity (14 days) on 1) the contractile properties of the soleus (Sol), an antigravity skeletal muscle; and 2) the myosin heavy chain (MHC) protein and mRNA isoform content of the Sol, vastus intermedius CVI), plantaris (Plan), and tibialis anterior (TA) muscles. The force-velocity relationships of the flight Sol muscles had a significant reduction in maximal isometric tension (-37%) and a corresponding increase in maximal shortening velocity (+20%). Additionally, the force-frequency relationship of the flight Sol muscles was shifted to the right of the ground-based control group. Microgravity had the greatest effect on muscle fiber composition in the Sol muscle, with a reduction in slow muscle fibers and a corresponding increase in muscle fibers categorized as hybrid fibers. The estimated absolute MHC isoform content was altered to the greatest extent in the Sol and VI muscles, with significant decreases and elevations in the slow type I and fast type IIX MHC protein isoforms, respectively. Consistent with the protein data, both the flight Sol and VI muscles exhibited significant elevations in the fast type IIX MHC mRNA isoform. In contrast, however, the flight Plan and TA groups had significant increases in the fast type IIB MHC mRNA isoform content without corresponding changes at the protein level. The results of this study suggest that spaceflight of even short duration produces important changes in the contractile properties of antigravity skeletal muscle. These changes are mediated by alterations in MHC phenotype and reductions in muscle mass. In some instances, the alterations in MHC mRNA isoform content seemed to be uncoupled from those occurring at the protein level. This apparent uncoupling between mRNA and protein expression demonstrates that the effects of microgravity must be better understood at the transcriptional, translational, and post translational levels.