Dependence of Na,K-ATPase and electrogenic component of Em in cultured myotubes on cell fusion

This study was undertaken in order to determine the relation among cell fusion, [3H]ouabain binding and the membrane potential (Em) of cultured rat skeletal muscle. The amount of ouabain bound and the Em both increased with age, the increases being most dramatic following fusion. Inhibition of fusion prevented the developmental increases in both properties of cultured muscle. After fusion, the size of the electrogenic component of Em, determined by the decrease in Em produced by ouabain within 5-10 min, increased independent of the age at which fusion occurred. It is concluded that the increase in Em with age depends on postfusion appearance and activity of Na,K-ATPase.