ABSTRACT
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 cross-sectional 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-month-old 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.