The effect of magnetic stimulation on unloaded soleus muscle of rat: changes in myosin heavy chain mRNA isoforms

This study assessed the potential application and the effectiveness of functional magnetic stimulation (FMS) for preventing skeletal muscle atrophy in adult rats. FMS using magnetic stimulator was performed to rat soleus muscle by placing a round magnetic coil on the back of 3(rd)-5(th) lumbar vertebral level at 20 Hz frequency for 60 min/day up to 10 days. A reverse transcriptase-polymerase chain reaction was applied to evaluate relative amounts of mRNAs specific to four myosin heavy chain (MHC) isoforms [MHCI beta, MHCIIa, MHCIIb, and MHClld(x)] in rat soleus muscle during contractile activity by magnetic stimulation. Ten-day unloading by hindlimb suspension induced a drastic decrease of MHCI beta and MHCIIa mRNA expressions, while MHCIIb and MHClld(x) mRNA was not decreased. The magnetic stimulation resuscitated the down-regulation of the mRNA levels of MHCI beta and MHCIIa. These results suggest that magnetic stimulation on acute atrophied muscles is useful for preventing the muscle atrophy.