Exercise training differentially modifies age-associated alteration in expression of Na+-K+-ATPase subunit isoforms in rat skeletal muscles

The present study tests the hypothesis that endurance exercise training (ETr) reverses age-associated alterations in expression of Na+-K+-ATPase subunit isoforms in rat skeletal muscles. Expression of the isoforms was examined in 16-mo-old sedentary middle-aged, 29-mo-old sedentary senescent, and 29-mo-old treadmill exercise-trained senescent Fischer 344 × Brown Norway rats. Levels of the α1-isoform increased with age in red gastrocnemius (GR), white gastrocnemius (GW), and extensor digitorum longus (EDL) muscles, and ETr further increased its levels. Levels of the α2-isoform were unchanged in GR, had a strong trend for a decrease in GW, and decreased significantly in EDL. ETr increased expression of the α2-isoform in all three muscle groups. There was no increase in expression of the β1-isoform in GR, GW, or EDL with age, whereas ETr markedly increased its levels in the muscles. There was a marked decrease with age in expression of the β2-isoform in the muscle groups that was not reversed by ETr. By cont...