Reactive oxygen species (ROS) are involved in control of many principle cellular processes, such as cell growth, metabolism, differentiation and apoptosis. In skeletal muscle, damaging action of ROS could be one reason for age-dependent sarcopenia. On the other hand, ROS could play a physiological role as second messengers modulating proliferative process. Molecular mechanisms underlying physiological or pathological action of ROS in skeletal muscle are still unknown. Since cultured muscle cells represent a convenient model to explore molecular mechanism of ROS signalling, the main aim of the current study was to investigate the action of ROS on the proliferative potential of myoblasts and their ability to differentiate into myotubes.

To this end, murine satellite cells obtained from young animals were cultured and aged in vitro. The proliferative capacity and the efficiency of differentiation of young and old cells were evaluated after the treatment with the diffusible and cell permeable ROS H₂O₂. A single 30 min long episode of oxidative stress induced by 3 mM H₂O₂ stimulated proliferation of young cells. Interestingly, the same concentration of ROS decreased the proliferation of old myoblasts. The higher (100 mM) concentration of H₂O₂ did not change the proliferative ability of young cells but decreased the proliferation of the old ones. Both concentrations of H₂O₂ did not affect significantly the differentiation of myoblasts into myotubes.

Experiments performed using patch-clamp technique in current clamp mode indicated that H₂O₂ increased spontaneous electrical activity of myotubes and facilitated anode break excitation.

Using Ca²⁺ imaging experiments with Fura-2AM we found that 5 min application of 100 mM H₂O₂ induced fast Ca²⁺ transients in a fraction of young myoblasts and elicited slow long-lasting signals in old myoblasts. Only old but not young myotubes responded to H₂O₂. Our data indicate differential effects of H₂O₂ on young versus old muscle cells, supporting the contribution of ROS signalling in skeletal muscle ageing. Long lasting Ca²⁺ signals could potentially underlie the damaging action of ROS in old cells.