Myosin isoenzymes in fast‐twitch and slow‐twitch muscles of normal and dystrophic mice.
Myosin isoenzymes in fast‐twitch and slow‐twitch muscles of normal and dystrophic mice.
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正常和营养不良小鼠快肌和慢肌中的肌球蛋白同工酶。
DOI：
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发表时间：
1983
期刊：
影响因子：
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通讯作者：
J. Hoh
中科院分区：
文献类型：
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作者：
R. Fitzsimons;J. Hoh
对正常和营养不良小鼠（129rejdy /dy）快缩肌和慢缩肌的天然肌球蛋白同工酶组成、肌球蛋白轻链分布和组织化学特征进行了分析，结果与已知的营养不良小鼠肌肉收缩异常相关。正常小鼠慢抽动比目鱼肌含有两种异肌球蛋白（慢肌球蛋白SM和中肌球蛋白IM），它们在电泳上与快抽动指长伸肌（e.d.l）的三种主要异肌球蛋白（FM1, FM2, FM3）不同。pH为9.2时，FM1、FM2、FM3和IM的钙激活的atp酶活性都远高于SM，这种差异反映在肌肉的组织化学特征上，正如在碱性pH. E.d.l下的肌原纤维atp酶反应所证明的那样。在pH为4.6的组织化学切片预培养后，II型纤维保留了肌原纤维atp酶活性，因此被分类为IIB型，而比目鱼II型纤维则没有，被分类为IIA型。结论是，I型（慢）纤维含有SM， IIA型（中间）纤维含有IM， IIB型（快）纤维含有FM1 - FM3。每种电泳上不同的肌球蛋白含有五种骨肌球蛋白轻链（LCs）的不同组合。因此，不同的正常肌肉，其异肌球蛋白谱不同，其轻链组成也不同。对营养不良肌肉中天然肌凝蛋白（FM1、FM2、FM3、IM、SM，按凝胶迁移速率递减的顺序排列）分布的分析显示，与相应的正常肌肉的分布相比，较慢迁移形式的比例增加。异肌球蛋白分布的改变可以解释小鼠营养不良肌肉中肌球蛋白轻链（LCf3）比例的已知减少。异肌球蛋白在营养不良肌肉中的异常分布与其组织化学特征的改变有关，并与其等距和等渗特性的异常有关。结果表明，与正常肌肉相比，鼠肌营养不良时异肌球蛋白分布的改变会导致单位肌质量输出功率的降低。这种可能性被认为是支配神经髓鞘的缺陷可能通过阻止高频脉冲到达肌肉而导致这些异常。
An analysis of the native myosin isoenzyme composition, myosin light‐chain distribution and histochemical profile of fast‐twitch and slow‐twitch muscles of normal and dystrophic (129 REJ dy/dy) mice has been performed, and the results correlated with the known contractile abnormalities of murine dystrophic muscles. Normal mouse slow‐twitch soleus contained two isomyosins (slow myosin, SM and intermediate myosin, IM) which were electrophoretically distinct from the three major isomyosins (FM1, FM2, FM3) of fast‐twitch extensor digitorum longus (e.d.l.) muscle. The calcium‐activated ATPase activities of FM1, FM2, FM3 and IM at pH 9.2 were each much higher than that of SM, and this difference is reflected in the histochemical profile of muscle, as demonstrated with the myofibrillar ATPase reaction at alkaline pH. E.d.l. Type II fibres retained myofibrillar ATPase activity following pre‐incubation of histochemical sections at pH 4.6, and were therefore classified Type IIB, whereas soleus Type II fibres did not, and were classified Type IIA. It was concluded that Type I (slow) fibres contain SM, Type IIA (intermediate) fibres contain IM, and Type IIB (fast) fibres contain FM1‐FM3. Each electrophoretically distinct myosin contained a different combination of the five skeletal myosin light chains (LCs). Thus different normal muscles, which differed in their isomyosin profiles, differed also in their light‐chain composition. Analysis of the distribution of native myosins (FM1, FM2, FM3, IM, SM, in order of decreasing gel migration rate) in dystrophic muscles revealed increased proportions of the slower‐migrating forms, when compared with the distribution in the corresponding normal muscles. The shift in isomyosin distribution would explain the known decrease in the proportion of myosin light chain (LCf3) in murine dystrophic muscle. The abnormal isomyosin distribution in the dystrophic muscle is correlated with its altered histochemical characteristics, and with well‐established abnormalities in its isometric and isotonic properties. It is concluded that the altered isomyosin distribution in murine dystrophic muscle would result in decreased power output per unit muscle mass when compared with normal muscle. The possibility is considered that defective myelination of the innervating nerve may contribute to these abnormalities by preventing higher frequency impulses from reaching muscle.