Fatigue resistance of rat extraocular muscles does not depend on creatine kinase activity.
Fatigue resistance of rat extraocular muscles does not depend on creatine kinase activity.
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大鼠眼外肌的抗疲劳能力不依赖于肌酸激酶活性。
DOI：
10.1186/1472-6793-5-12
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发表时间：
2005-08-17
期刊：
影响因子：
--
通讯作者：
Andrade FH
中科院分区：
文献类型：
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作者：
McMullen CA;Hayess K;Andrade FH
肌酸激酶(CK)将能量储存系统磷酸肌酸与细胞ATPase联系起来。CK活性是ATP含量的时间和空间缓冲，尤其是在快速抽动的骨骼肌中。眼外肌是出了名的快速和活跃，这表明需要有效的ATP缓冲。本研究验证了以下假设：(1)大鼠眼外肌CK亚型的表达和活性较高，以及(2)这些肌肉对疲劳的抵抗力取决于CK活性。我们发现胞浆和线粒体CK亚型的mRNA和蛋白水平在眼外肌中低于趾长伸肌(EDL)。眼外肌CK总活性相应降低。此外，免疫细胞化学和免疫印迹显示，肌瘤M系的细胞骨架成分在眼外肌中下调，其中发现了一小部分CK活性。CK抑制显著加快了EDL肌束疲劳的发展，但对眼外肌的影响不大。为了寻找替代的ATP缓冲液来弥补眼外肌中CK的相对缺乏，我们确定了两种腺苷酸激酶(AK)亚型的mRNAs在这些肌肉中表达水平较高。EDL和眼外肌的总AK活性相似。这些数据表明，眼外肌的特征疲劳抵抗力不依赖于CK活性。
Creatine kinase (CK) links phosphocreatine, an energy storage system, to cellular ATPases. CK activity serves as a temporal and spatial buffer for ATP content, particularly in fast-twitch skeletal muscles. The extraocular muscles are notoriously fast and active, suggesting the need for efficient ATP buffering. This study tested the hypotheses that (1) CK isoform expression and activity in rat extraocular muscles would be higher, and (2) the resistance of these muscles to fatigue would depend on CK activity. We found that mRNA and protein levels for cytosolic and mitochondrial CK isoforms were lower in the extraocular muscles than in extensor digitorum longus (EDL). Total CK activity was correspondingly decreased in the extraocular muscles. Moreover, cytoskeletal components of the sarcomeric M line, where a fraction of CK activity is found, were downregulated in the extraocular muscles as was shown by immunocytochemistry and western blotting. CK inhibition significantly accelerated the development of fatigue in EDL muscle bundles, but had no major effect on the extraocular muscles. Searching for alternative ATP buffers that could compensate for the relative lack of CK in extraocular muscles, we determined that mRNAs for two adenylate kinase (AK) isoforms were expressed at higher levels in these muscles. Total AK activity was similar in EDL and extraocular muscles. These data indicate that the characteristic fatigue resistance of the extraocular muscles does not depend on CK activity.