STIMULATION OF ACTIVE TRANSEPITHELIAL SODIUM-TRANSPORT IN ISOLATED FROG-SKIN BY HYDROGEN-PEROXIDE

The influence of reactive oxygen metabolites on ion transport across the plasma membrane was investigated by measuring the effect of hydrogen peroxide (H2O2) on short-circuit current (SCC) and transepithelial conductance (G(t)) in isolated frog skin. This cellular system gives access to the apical (outer) and basolateral (inner) membranes of the polarized epithelial cells. Both apical and basolateral addition of H2O2 (10-mu-M to 100 mM) induced a dose-dependent stimulation of SCC. This stimulation could be blocked by amiloride in the apical solution, showing that the H2O2-induced stimulation of SCC was a result of increased active transepithelial sodium (Na) transport. The increase in Na transport was prevented by addition of catalase, consistent with a role for H2O2 in producing this effect. The mechanisms for H2O2-stimulated Na transport localized in the apical and basolateral membranes differ markedly. Basolateral H2O2-stimulated Na transport was inhibited by indomethacin, indicating that increased prostaglandin synthesis was responsible for this effect. Apical H2O2 stimulation of Na transport was not affected by indomethacin, nor did H2O2 interfere with the Na self-inhibition of the Na channels. It is concluded that apical H2O2 increases the Na permeability of the apical membrane, either through direct interaction with the apical Na channels or indirectly through products of lipid peroxidation.