[Ouabain-insensitive K+ and Na+ fluxes in frog muscle]

Potassium and sodium fluxes in frog muscles incubated in K- and Na-free Mg2+ or choline-substituted Ringer solution were studied. Ouabain (10(-4) M) increased the potassium and decreased the sodium efflux. It was shown, that the increase of the potassium efflux was not due to changes in membrane electrical properties of inhibition of "back pumping" of potassium ions leaking out of the cells. It is supposed that potassium ions are translocated by K-carrier phosphorylated with inorganic phosphate. As known, ouabain accelerates this type of phosphorylation, that is why the potassium efflux increases. In a medium with or without ouabain sodium ions are translocated by Na-ATPase without participation of external potassium ions. Thus sodium and potassium fluxes carried out by membrane ATPase systems are not coupled.