On the amount of (Na+ + K+)-ATPase available for transepithelial sodium ion transport in the amphibian skin.

Pretreatment of frog skin epithelium homogenates with sodium dodecyl sulphate in the presence of ATP reveals levels of ouabain-sensitive ATPase activity usually higher and occasionally far higher than those required to sustain maximum rates of Na+ transport. This supports the view that Na+ transport involves only a fraction of the epithelial cells.