Adaptation of mouse skeletal muscle to a novel functional overload test: changes in myosin heavy chains and SERCA and physiological consequences.

B Awede, A Berquin, F Wuytack, J Lebacq
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引用次数: 18

Abstract

We have used a new approach to study the effects of overload on skeletal muscle phenotype in mice. The method used avoids any traumatising contact with muscles and the inflammatory reaction that this may provoke. Blocks of lead embedded in silicone were inserted under the skin of the lower part of the back. After 1 month, a 17% hypertrophy was found to have occurred in the tonic soleus muscle, but no change was observed in the fast-twitch extensor digitorum longus (EDL) muscle. The main effects on the contractile properties of the soleus muscle were a decrease in the tetanic relaxation rate and a reduction in the maximal velocity of shortening. Immunohistological analysis of the soleus muscles revealed an increase in the proportion of fibres that express myosin heavy chain (MHC) 1, from 54.2% to 73.9%, with a reduction in the proportion of MHC2a-positive fibres, from 45.8% to 30.2%. These changes were accompanied by an increase in the proportion of fibres that express the slow type of sarcoplasmic reticulum calcium pump (SERCA2a), from 61.8% to 84.7%. In EDL muscles, overload induced only minor changes. Thus, this method of overload affected the soleus muscle in particular. The observed changes in the control of muscle contraction were significantly larger than the changes in typical myofibrillar properties that were observed. These results indicate that there is a temporal dissociation between the relative expression of MHCs and SERCAs.

小鼠骨骼肌对一种新型功能过载测试的适应:肌球蛋白重链和SERCA的变化及其生理后果。
我们采用了一种新的方法来研究过载对小鼠骨骼肌表型的影响。使用的方法避免了任何创伤性的肌肉接触和可能引起的炎症反应。将嵌在硅胶中的铅块插入背部下部的皮肤下。1个月后,发现强直性比目鱼肌发生17%的肥大,但在快速收缩的指长伸肌(EDL)肌中未观察到变化。对比目鱼肌收缩特性的主要影响是强直松弛率的降低和最大缩短速度的降低。比目鱼肌的免疫组织学分析显示,表达肌球蛋白重链(MHC) 1的纤维比例从54.2%增加到73.9%,mhc2a阳性纤维比例从45.8%减少到30.2%。这些变化伴随着表达慢型肌浆网钙泵(SERCA2a)的纤维比例的增加,从61.8%增加到84.7%。在EDL肌肉中,过载只引起轻微的变化。因此,这种超负荷的方法尤其影响比目鱼肌。观察到的肌肉收缩控制的变化明显大于观察到的典型肌纤维特性的变化。这些结果表明mhc和SERCAs的相对表达在时间上存在分离。
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