Training-induced ROS production and adaptations in rat skeletal muscles

Ten male 2-month-old rats were trained to run on a treadmill up to ~55% of their maximal oxygen uptake for 1 h/day, 3 days/week, 14 weeks. Ten age-matched sedentary rats were used as controls. Rats were sacrificed 24 h after the last training session in order to study the effect of such moderate aerobic training on two skeletal muscles differing in fiber type and metabolism: Soleus and Tibialis Anterior. The aim was to evaluate whether moderate endurance training i) induced fiber-type and metabolic adaptations; ii) caused oxidative stress; iii) upregulated anti-oxidant and cytoprotective molecules. A variety of analyses were carried out, ranging from morphometric and histochemical evaluations, RT-PCR analysis of relevant gene expression, western blotting, assessment of plasma membrane and sarcoplasmic reticulum calcium channels and ionic pump activities, quantification of ROS-induced modifications, enzymatic assays. Data showed that the effects of moderate training were similar to that described for intensive training as far as the metabolic and functional adaptations of fast-twitch muscles were concerned, but that also slow-twitch muscles were affected by training in somewhat similar ways. The formation of moderate amounts of ROS was documented even in this model of moderate exercise training. Moreover, ROS thus formed were shown to induce defensive responses but also to be responsible of - or to participate in - the induction of most adaptive training-related modifications