Effect of microgravity on the expression of mitochondrial enzymes in rat cardiac and skeletal muscles
Effect of microgravity on the expression of mitochondrial enzymes in rat cardiac and skeletal muscles
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DOI：
10.1152/jappl.1998.84.2.593
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发表时间：
1998-02-01
影响因子：
3.3
通讯作者：
Hood, DA
中科院分区：
文献类型：
--
作者：
Connor, MK;Hood, DA
本研究的目的是研究短期微重力暴露对心肌和骨骼肌(三头肌)核基因和线粒体基因表达的影响。将6只成年雄性大鼠暴露在微重力环境中6天，并与6只地面对照动物进行比较。我们观察到心脏苹果酸脱氢酶(MDH)活性在微重力暴露后显著增加了32%，同时心脏MDH基因水平也增加了62%。尽管在微重力作用下，编码III、TV和Vic亚基的mRNAs略有增加，并且IV亚基的蛋白质含量增加了2.2倍，但心脏细胞色素C氧化酶(CytOx)的活性保持不变。在骨骼肌中，MDH的表达不受微重力的影响，但CytOx活性在微重力下显著降低41%，而亚基III、TV和Vic的mRNA水平和亚基TV蛋白水平没有变化。因此，组织特有的(即心脏和骨骼肌)在微重力下对核编码的线粒体蛋白的调节存在差异。此外，细胞核编码蛋白的表达，如CytOx亚单位TV和MDH的表达在组织内受到差异调控。我们的数据还表明，心脏经历了以前未知的线粒体适应，以应对短期微重力条件，比骨骼肌明显的适应更剧烈。为了应对微重力，有必要进一步研究评估这些适应在心脏中的功能后果，以及那些旨在测量蛋白质周转的研究。
The purpose of this study was to examine the expression of nuclear and mitochondrial genes in cardiac and skeletal muscle (triceps brachii) in response to short-duration microgravity exposure. Six adult male rats were exposed to microgravity for 6 days and were compared with six ground-based control animals. We observed a significant 32% increase in heart malate dehydrogenase (MDH) enzyme activity, which was accompanied by a 62% elevation in heart MDH mRNA levels after microgravity exposure. Despite modest elevations in the mRNAs encoding subunits III, TV, and VIc as well as a 2.2-fold higher subunit IV protein content after exposure to microgravity, heart cytochrome c oxidase (CytOx) enzyme activity remained unchanged. In skeletal muscle, MDH expression was unaffected by microgravity, but CytOx activity was significantly reduced 41% by microgravity, whereas subunit III, TV, and VIc mRNA levels and subunit TV protein levels were unaltered. Thus tissue-specific (i.e., heart vs. skeletal muscle) differences exist in the regulation of nuclear-encoded mitochondrial proteins in response to microgravity. In addition, the expression of nuclear-encoded proteins such as CytOx subunit TV and expression of MDH are differentially regulated within a tissue. Our data also illustrate that the heart undergoes previously unidentified mitochondrial adaptations in response to short-term microgravity conditions more dramatic than those evident in skeletal muscle. Further studies evaluating the functional consequences of these adaptations in the heart, as well as those designed to measure protein turnover, are warranted in response to microgravity.