Effects of Dynamic and Static Loads on the Concentration of Sodium and Potassium in Murine Skeletal Muscles

The effects of dynamic and static load on the intracellular concentrations of sodium $\left({\mathrm{Na}}_{\mathrm{i}}^{+}\right)$ and potassium (K⁺_i) in m. soleus and m. biceps, respectively, were studied in mice. Both dynamic (swimming for 60 min) and static (hanging on the grid for 40 min) load led to a 2-fold increase in ${\mathrm{Na}}_{\mathrm{i}}^{+}$ level, a decrease in K⁺_i concentration by 25-35%, and 3-4-fold increase in the ${\mathrm{Na}}_{\mathrm{i}}^{+}/{\mathrm{K}}_{\mathrm{i}}^{+}$ ratio. These effects of dynamic and static loads on the studied parameters remained unchanged in mice subjected to regular physical exercise (swimming or hanging on the grid for 1 h a day over 4 weeks). Our results suggest that dissipation of sodium and potassium transmembrane gradients during physical exercise can be considered as a factor of regulation of functional activity of skeletal muscles, which includes changes in transcription and translation of myokines observed previously.