【作者】 袁建琴；

【导师】 王瑞元；

【作者基本信息】 北京体育大学 ， 运动人体科学， 2004， 博士

【摘要】 本研究目的在于从肌肉特异性骨架蛋白desmin的角度探讨离心运动造成的骨骼肌损伤,同时观察低氧对肌肉损伤的影响。采用128只、7周龄雌性SD大鼠为实验对象,一次性跑台离心运动至力竭的损伤模型,跑台坡度为-16°,速度16米/分。低氧组动物放置在氧分压为12.7%的低氧舱中(相当于海拔4000米高度)。低氧组动物先在低氧舱中适应3天,然后分为低氧安静对照即刻、1、2、4、7天组和低氧力竭运动后即刻、1、2、4、7天组。常氧组设安静对照组和一次性力竭运动后即刻、1、2、4和7天组。动物分组共计16组,每组8只大鼠,所有动物力竭运动均在常氧环境下进行。本文主要结果为:(1)离心运动后肌纤维局部desmin染色不同程度、不同范围地出现了变淡、模糊、甚至缺失,出现desmin阴性纤维,表明desmin细胞骨架破坏是离心运动诱导损伤的形态学标志。(2) Desmin免疫组化染色可以作为评估骨骼肌早期损伤的工具。离心运动力竭后desmin免疫组化染色下降从即刻开始,是损伤早期的表现,且预示着肌纤维进一步损伤和坏死。在离心运动后第4天或更早,部分肌原纤维启动重建,损伤后的恢复过程中desmin表达的增加可能与肌原纤维重建有关。(3) desmin表达主要在转录水平调节,离心运动后desmin mRNA下调。(4) 离心运动后Calpain总活性升高,激活的Calpain开始选择性降解底物蛋白,desmin降解随之增加,desmin纤维丝断裂,肌原纤维的固定丧失,引起Z线流和A带紊乱。另外,Calpain自溶降解生成的多肽片断可能成为化学趋化剂,与中性粒细胞对损伤的早期应答有关。(5) 从力竭运动时间、desmin蛋白和mRNA表达、Calpain酶活性变化、炎症细胞浸润等几个方面,分析本实验条件下的低氧对离心运动所致损伤的影响,发现各方面的变化趋势基本一致,表明低氧和常氧状态下大鼠骨骼肌损伤进程相似,低氧不能明显加速或加深损伤。更多还原

【Abstract】 The purpose of this study was to investigate skeletal muscle injury induced by eccentric exercise from the angle of desmin cytoskeleton and to observe effects of hypoxia on muscle injuries. 128 female SD rats of 7-week old were adopted as the objects of this study and the model of injury for a bout of exhaustive eccentric exercise on a treadmill. The gradient of the treadmill was -16°and the speed was 16m/min. The rats were randomly divided into the hypoxic groups, which was placed in the hypoxic cabin with the PO2 of 12.7%, corresponding to the altitude of 4000m. They were accommodated to this condition for 3 days first, and then they were divided into the hypoxic sedentary control groups (killed on 0,1,2,4,7 days after exercise) and hypoxic exhaustive exercise groups (killed immediately and on 1,2,4,7 days after hypoxic exhaustive exercises). As for the normoxic groups there were one sedentary control group and five exhaustive exercise groups (killed immediately and on 1,2,4, 7 days after a bout of exhaustive exercise). In this study,there were sixteen groups of rats, eight in each group. All the rats in the exercise groups performed exhaustive exercises under normoxic condition.The main results of this study are as follows:(1) After eccentric exercises staining for desmin in part of muscle fibers faded and obscured in different degree and to different extent. It was even lost and negative fibers of desmin occurred, showing that the damage of desmin cytoskeleton is the morphological sign of injuries induced by eccentric exercises. (2) Immunohistochemical staining of desmin was proven to be a tool for estimating the early injury of skeletal muscles. Decrease of desmin staining started immediately after exhaustive eccentric exercise, which was the early representation of injuries and indicated that the muscle fibers would be further injured and become necrosis. The remodeling of part of fibers started on the 4 days after exercise or earlier. During the recovery of injury, the increase of desmin expression is likely to be related to the remodeling of myofibrils.(3) The expression of desmin was mainly regulated at the transcriptional level and the contents of desmin mRNA decreased after eccentric exercise (4) The total activity of calpain in skeletal muscles increased immediately after the eccentric exercise, The activated calpain started to selectively degradate protein substrate, followed by the increase of desmin degradation, the breakdown of desmin filament, the loss of myofibrillar <WP=7>registry, which resulted in the disorder of the Z-line streaming as well as the A-band. In addition, the polypeptide fragments produced by calpain autolysis were likely to become chemoattractant, which was related to the early response of the neutrophils on injuries. (5) Analyzing the influence of hypoxia under the condition of this experiment on injuries induced by eccentric exercises from the aspects of the duration of the downhill running until exhaustion on the treadmill,the expression of desmin and desmin mRNA, the change of the calpain activity, the infiltration of inflammatory cell, it was found that the trends of those changes were basically consistent, showing that the process of the skeletal muscle injuries of rats under the hypoxic condition is consistent with those under the normoxic condition and that the hypoxia is unable to obviously accelerate or deepen the injuries.更多还原