MyoD, Myogenin and Myosin Heavy Chain mRNA Expression in Rat Skeletal Muscle after a Single Session of Low-Intensity Treadmill Exercise

[Purpose] We examined the time course of changes in the activation of muscle satellite cells and muscle protein synthesis after a single session of low-intensity treadmill exercise. [Subjects] A total of 25 male Wistar rats aged 11 weeks were used. [Methods] Rats were run on a treadmill with a 16° decline for 30 min at 24 m/min, except for the control group (CON). Blood was collected to measure creatine phosphokinase (CPK) and both soleus muscles were removed to analyze histological and muscle gene expression at 24, 48, 72 and 96 h post-exercise. [Results] CPK levels in exercised rats at 24 and 96 h were significantly higher than in CON, and CPK levels at 96 h were higher than those at 48 h. Infiltration of macrophages and gathering of small myofibers were detected in the exercise group, but there were no significant differences in MyoD, myogenin, myosin heavy chain (MHC) -1 and MHC-2a mRNA levels. [Conclusion] These results suggest that muscle satellite cells and muscle protein synthesis are not significantly activated, despite the occurrence of myotrauma, in the acute phase (24 h to 96 h) after a single session of low-intensity exercise.