中文摘要：

目的：观察缺氧及缺氧复合运动条件下大鼠比目鱼肌肌球蛋白重链（MHC）异构体组成的变化。方法：Wistar大鼠随机分为4组：平原对照组、缺氧组、平原运动组和缺氧复合运动组。缺氧复合运动组大鼠持续暴露于模拟海拔5000m高原5周，每天降至4000m高原进行游泳运动1h（6d／week），运动结束后回升至5000m；缺氧组大鼠同时在低压舱内相同海拔高度饲养，但不进行游泳运动；平原运动组和平原对照组在舱外同时饲养，其中平原运动组每天进行游泳运动1h（6d／week）。在末次运动结束后24h处死大鼠，分离后肢比目鱼肌。用含30％甘油的SDS-PAGE电泳分离比目鱼肌MHC异构体，观察MHC异构体组成变化。结果：平原游泳运动大鼠比目鱼肌重量指数增加，而缺氧复合运动组与平原对照比较无显著差异；大鼠比目鱼肌中段MHC主要由Ⅰ（78％）、Ⅱa（22％）2种异构体组成，缺氧组比目鱼肌MHC由Ⅱa向Ⅰ型转变，单纯运动和缺氧复合运动组与缺氧组变化趋势相同，但缺氧复合运动组显著低于单纯运动组。结论：慢性缺氧和运动训练后，大鼠比目鱼肌肌纤维MHC组成向能量利用效率更高的慢收缩肌纤维Ⅰ型转变，提示慢性缺氧和缺氧复合运动后比目鱼肌能量利用效率增加。

英文摘要：

AIM： To determine the effects of chronic hypobaric hypoxia and combined with exercise on myosin heavy chain （MHC） profile in rat soleus. METHODS： Wistar rats were divided into 4 groups： control （C）, hypoxic group （H） , exercising group （E） and hypoxia - combined with exercise group （HE）. Rats in H and HE groups were subjected to simulated 5 000 m hypobaric hypoxia for 5 weeks （24 h/d, 7 d/week）, except that animals of both groups were descended to 4 000 m for 1 h/day （6 d/week） from the second week to the end, during which the HE group was forced to swim ceaselessly. Twenty -four hours after the last bout of exercise training, animals were sacrificed at 4 000 m （ H and HE groups） or at sea level （ C and E groups）, soleus was collected and MHC was determined with sodium dodecyl - polyacrylamide gel electrophoresis followed by densitometry analysis. RESULTS ： The composition of myosin heavy chain in rat soleus was type Ⅰ （78%） and type Ⅱa （22%） in C. The percentage of myosin containing the type Ⅰ isoform in rat soleus was significantly higher in H, E and HE groups than that in the control. CONCLUSION： The switch of MHC isoforms in soleus from type Ⅱ a to type Ⅰ is advantageous in improving efficiency of energy utilization. These changes may reflect the trend of increasing capacity duration and energy utilization efficiency of rat soleus after hypoxia and hypoxia - combined exercise training.