Effect of ouabain on electrical conductance of frog skins. Evidence against recycling of sodium.

Ouabain (10(-4) M) added to the serosal solution of isolated frog skin not only stops the active transport of Na+ but causes a dramatic increase in the electric conductance of the skin. The effect also appears when ouabain is added to amiloride-pretreated skins, ruling out the possibility of a cellular effect. The similarity between the effect of ouabain on normal and amiloride-pretreated skins indicates that no appreciable recycling of Na+ across the basolateral membrane of frog skin takes place. The change of Na+ efflux after ouabain is added to amiloride-pretreated skins parallels the change of electric conductance, indicating that besides blocking the Na+ pump, ouabain affects the paracellular shunt pathway between the cells.