大鼠比目鱼肌肌纤维总数、横截面积及其内慢肌纤维和快肌纤维横截面积与年龄相关的变化

目的 探讨SD大鼠比目鱼肌的形态学特征随年龄增长的变化情况。方法 4、18、25和30月龄雄性SD大鼠比目鱼肌各5块，通过HE染色、琥珀酸脱氢酶（SDH）活性检测和免疫组织化学方法，观测比目鱼肌纤维形态、数目、肌肉横截面积及其内慢肌纤维和快肌纤维分布特征、横截面积与年龄相关的变化。 结果 比目鱼肌内肌纤维形状随年龄增长变得不规则，并伴以肌纤维劈裂和簇聚。30月龄较4月龄大鼠的比目鱼肌纤维总数减少（P＜0.05），而且其与其余年龄组大鼠的肌肉横截面积比较亦明显减小（P＜0.01）。仅4月龄和25月龄大鼠比目鱼肌内慢肌纤维横截面积相比无差别（P＞0.05），而快肌纤维横截面积则表现为18月龄和25月龄比较无差异（P＞0.05）。结论 30月龄SD大鼠比目鱼肌纤维总数、肌肉横截面积及其内慢肌纤维和快肌纤维横截面积与其他年龄组大鼠相比差异显著，提示在衰老后期骨骼肌功能可能会发生明显变化。

Age-related changes in the total number of muscle fibers,cross-sectional areas of the muscle and slow and fast muscle fibers in the rat soleus muscle

Objective To investigate morphological changes of the soleus muscle of SD rats with various ages. Methods The shape and total number of muscle fibers, and cross sectional area (CSA) the soleus muscle of 4-, 18-, 25- and 30-month old male SD rats (5 muscles in each age group) as well as the distributional characteristics and CSA of slow and fast muscle fibers were observed and measured using hematoxylin and eosin staining, succinate dehydrogenase activity assay and immunohistochemistry. Results The shape of muscle fibers in the soleus became irregular with advancing age, combined with splitting and grouping of muscle fibers. The total number of muscle fibers in 30-month soleus reduced significantly compared with that of 4-month muscle (P＜0.05) and the CSA of 30-month soleus also decreased in comparison with that of the other age groups (P＜0.01). The CSA of slow muscle between 4-month and 25-month and the CSA of fast muscle fibers between 18-month and 25-month groups showed no difference (P＞0.05). Conclusion The total number of muscle fibers in soleus and CSA of soleus, slow and fast muscle fibers in soleus in 30 month SD rat significantly decline compared with those at the other ages. It probably implies that the serious dysfunctional changes may happen to skeletal muscle in the late stage of aging.