The amphibian skin and other isolated epithelial systems are classical model objects for studying the mechanisms of transepithelial ion transport. In their ability to transport electrolytes and in response to some hormones, the amphibian skin and bladder are similar to the distal renal tubules ; this allows the data for these model objects to be used for clarifying the mechanisms of water and ion transports in renal cells. The Na+ transport in osmoregulatory epithelia is a complex multicomponent system providing the establishment and maintenance of electrolytic and water homeostasis. The key sodium transport proteins, such as amiloride-sensitive epithelial Na+ channels (ENaCs), Na+/K+ ATPases, and Na+/H+ exchangers, are targets for oxidative stress . However, the mechanisms underlying the effect of oxidants and reducing agents on individual components of the Na+ transepithelial transport are still unknown.