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 (H(2)O(2)) 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 H(2)O(2) (10 mum to 100 mm) induced a dose-dependent stimulation of SCC. This stimulation could be blocked by amiloride in the apical solution, showing that the H(2)O(2)-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 H(2)O(2) in producing this effect. The mechanisms for H(2)O(2)-stimulated Na transport localized in the apical and basolateral membranes differ markedly. Basolateral H(2)O(2)-stimulated Na transport was inhibited by indomethacin, indicating that increased prostaglandin synthesis was responsible for this effect. Apical H(2)O(2) stimulation of Na transport was not affected by indomethacin, nor did H(2)O(2) interfere with the Na self-inhibition of the Na channels. It is concluded that apical H(2)O(2) increases the Na permeability of the apical membrane, either through direct interaction with the apical Na channels or indirectly through products of lipid peroxidation.
Bjerregaard
H F
HF
Institute of Life Sciences and Chemistry, University of Roskilde, Denmark.