Muscle fiber necrosis and oxidative stress in disuse muscular atrophy

我们的研究目的是确定后肢悬吊是否会引起萎缩肌肉的坏死，以及氧化应激是否在这一过程中起作用。对Wistar大鼠（8周龄，雄性）卸车2周后和对照大鼠后肢肌肉进行光镜和电镜观察。悬吊大鼠股直肌、股内侧肌、股外侧肌、中间肌、腓肠肌、比目鱼肌的纤维直径均小于对照组，其中比目鱼肌的1型纤维和股外侧肌、股内侧肌的2B型纤维直径更小。悬吊大鼠股外侧肌、股内侧肌、腓肠肌头外侧及内侧肌、比目鱼肌深层均有坏死纤维，坏死纤维率（数/10）分别为：1.4、1.3、1.7、1.4、0.3、1.9。后肢悬吊后，用desmin和plectin单克隆抗体染色的网状结构不规则，电镜下肌原纤维排列和z带也不规则。后肢肌肉深部部分坏死纤维对超氧化物歧化酶单克隆抗体呈阳性反应。比目鱼肌的α -生育酚含量约为股直肌的40%。综上所述，后肢悬吊引起了富含氧化纤维的肌肉深层肌纤维坏死，废用性肌肉萎缩不仅表现为肌纤维直径的减少，还表现为肌肉动态过程的复杂化。虽然氧化应激可能与后肢悬吊后肌纤维坏死过程有关，但α-生育酚含量并不能揭示肌纤维坏死的全部机制。

The purpose of our study was to determine whether hindlimb suspension induce necrosis in the atrophied muscles and whether oxidative stress play any role in the process. Light and electron microscopic observation of hindlimb muscles of Wistar rats (8 weeks of age, male), which were unloaded for two weeks, and control rats were performed. The fiber diameters of the rectus femoris, vastus medialis, vastus lateralis, intermedius, gastrocnemius, soleus muscles of the suspended rats were smaller than those of the controls, especially type 1 fiber in the soleus muscle and type 2B fiber in the vastus lateralis and medialis muscles. Necrotic fibers were found in deep portions of the vastus lateralis, vastus medialis, lateral and medial heads of gastrocnemius, and soleus muscles of the suspended rats, and the following were the rate of necrotic fibers (number/10 rats) : 1.4, 1.3, 1.7, 1.4, 0.3, and 1.9, respectively. Reticular structures stained with monoclonal antibodies of desmin and plectin were irregular after hindlimb suspension, and irregularity of myofibrillar arragement and Z-bands was also found by electron microscopy. A few necrotic fibers in the deep portion of the hindlimb muscles had a positive reaction to the monoclonal antibody to superoxide dismutase. Alfa-tocopherol content of the soleus muscle was approximately 40% as much as that of the rectus femoris muscle. In conclusion, hindlimb suspension induces muscle fiber necrosis in the deep portion of the muscles, which were rich in oxidative fibers, and disuse muscle atrophy is not only decrease in muscle fiber diameter, but also complicated dynamic process of the muscle. Although oxidative stress may concern the process of necrosis after hindlimb suspension, α-tocopherol content did not reveal all mechanism of muscle fiber necrosis.