尾部悬吊与30月龄大鼠比目鱼肌的形态学特征比较

Comparison of Morphological Features in Soleus between Tail-suspended and 30-month-old Rats

目的观察尾部悬吊和30月龄大鼠比目鱼肌发生萎缩过程的异同点。方法SD雄性大鼠42只,随机分为7组,即尾部悬吊5d、7d、14d组,相应的同步对照和30月鼠龄组,在各时间点制备比目鱼肌横截面冰冻切片标本,用抗MHCⅡ单克隆抗体进行免疫组织化学染色,计算比目鱼肌Ⅰ、Ⅱ型肌纤维横截面积并计数各型肌纤维数目。结果与同步对照组相比,悬吊组大鼠比目鱼肌的湿重,相对湿重,Ⅰ、Ⅱ型肌纤维横截面积,经体重归一化的肌纤维横截面积均显著降低,Ⅱ型肌纤维比例显著增加,而Ⅰ型肌纤维比例减少。与14d对照组相比,30月龄组大鼠比目鱼肌湿重和Ⅰ、Ⅱ型肌纤维横截面积均明显增大,但其相对湿重和经体重归一化的肌纤维横截面积却显著降低,与悬吊14d组无显著差异。30月龄组大鼠比目鱼肌中Ⅰ、Ⅱ型肌纤维比例与各对照组相比亦无显著差异。结论30月龄大鼠比目鱼肌萎缩以首先出现相对湿重与归一化肌纤维横截面积降低为特征,且发生较慢,而尾部悬吊大鼠比目鱼肌则在较短时间内发生全面萎缩。

Objective To compare the morphological differences in soleus between tail-suspended and 30-month-old rats. Methods Fourty-two male rats were randomly divided into seven groups： 5 d, 7 d and 14 d tail-suspended and their synchronous control groups, 30-month-old group. The crosssectional area（CSA） and percentage of MHC Ⅰ/Ⅱ fibers were measured in immunohistochemically stained sections and CSA was normalized by body weight. Results Wet weight, relative wet weight, CSA and normalized CSA in unloaded soleus decreased significantly as compared with the synchronous control. The percentage of MHC I fibers decreased, but that of MHC Ⅱ fibers increased in unloaded soleus. The wet weight and CSA of soleus in 30-month-old rats increased, but the relative wet weight and normalized CSA reduced significantly as compared with 14-day synchronous control. The relative wet weight and normalized CSA of soleus in 30-month-old rat were similar to that of 14 d tail-suspended group. The percentage of MHC Ⅰ/Ⅱ fibers of soleus in 30-monthold rat and in 5 d, 7 d, and 14 d of synchronous control groups kept constant value. Conclusion It＇ s suggested that the atrophic process of soleus is slower in 30-month-old rats than that in the tail-suspended rates. The reduction of soleus relative wet weight and normalized CSA appears early in aged rats, but the absolute and relative wet weight of soleus decrease simultaneously in tail-suspended rats.