4 h/d站立可防止4周尾部悬吊大鼠比目鱼肌的萎缩

目的依据比目鱼肌湿重、不同型肌纤维横截面积及比例与聚丙烯酰胺凝胶电泳分离肌球蛋白重链(mvosin heavy chain，MHC)异构体比例的变化，评价4h／d站立是否可防止模拟失重下比目鱼肌的萎缩。方法雄性SD大鼠18只，按体重配对原则随机分为3组，每组6只：即对照组(CON)，尾部悬吊4周组(TS)及尾部悬吊 4h／d站立组(TS STD4)。4周后，取双侧肾上腺及比目鱼肌(soleus，SOL)，称取湿重。左侧SOL行冰冻切片，ATP酶钙钴法染色以观察骨骼肌肌纤维种类及横截面积。右侧SOL行组织匀浆，在70V、40C下，于8％凝胶上电泳28h，考马斯亮蓝染色，用Scion image软件对MHC条带进行光密度容积的测量，得出不同MHC异构体的比例。结果4周模拟失重导致双侧后肢骨骼肌SOL的湿重、Ⅰ型与Ⅱ型肌纤维横截面积、Ⅰ型肌纤维比例及MHCI的比例均显著降低(P＜0、01或P＜0．05)。4h／d间断性站立可完全防止比目鱼肌上述指标的变化，与CON组相比无显著差异(P＞0．05)。结论每日4h站立可完全防止模拟失重大鼠SOL萎缩。

Daily 4-h Standing Can Prevent Soleus Atrophy Induced by 4 Weeks Tail Suspension in Rats

Objective: To observe the effects of intermittent standing in counteracting the soleus atrophy induced by simulated microgravity. Method: Eighteen male Sprague-Dawley rats were randomly assigned to 3 groups: control (CON), four-week tail-suspension (TS), and TS plus daily 4 h standing (TS + STD4). After 4 weeks, bilateral adrenal glands and soleus muscle were dissected and weighed. The left soleus was sectioned with cryostat and stained with ATPase staining. The cross sectional area (CSA) of type I and II fibers and the relative proportion of type I fibers were measured using Leica image analysis system. The right soleus was homogenized and stained with Coomassie Brilliant Blue following electrophoresis on 8% SDS-PAGE under 70 V and < 4 degrees C for 28 h. The Scion image software was used to evaluate the result of the densitometry of different types of MHC. Result: In TS, wet weights of the soleus, CSA of type I and II fibers, and proportion of type I fibers decreased obviously, as compared with those rats in CON (P<0.01 or P<0.05). The SDS-PAGE showed similar results as by ATPase staining in the proportion of MHC I. Whereas in TS + STD4, there were no significant differences of those parameters compared with those rats in CON. Conclusion: Daily 4-h standing fully prevented the soleus atrophy induced by simulated microgravity for 4 wk in rats.