Hydrogen peroxide, potassium currents, and membrane potential in human endothelial cells.
BACKGROUND
Hydrogen peroxide (H2O2) and reactive oxygen species are implicated in inflammation, ischemia-reperfusion injury, and atherosclerosis. The role of ion channels has not been previously explored.


RESULTS
K+ currents and membrane potential were recorded in endothelial cells by voltage- and current-clamp techniques. H2O2 elicited both hyperpolarization and depolarization of the membrane potential in a concentration-dependent manner. Low H2O2 concentrations (0.01 to 0.25 micromol/L) inhibited the inward-rectifying K+ current (KIR). Whole-cell K+ current analysis revealed that H2O2 (1 mmol/L) applied to the bath solution increased the Ca2+-dependent K+ current (KCa) amplitude. H2O2 increased KCa current in outside-out patches in a Ca2+-free solution. When catalase (5000 micro/mL) was added to the bath solution, the outward-rectifying K+ current amplitude was restored. In contrast, superoxide dismutase (1000 u/mL) had only a small effect on the H2O2-induced K+ current changes. Next, we measured whole-cell K+ currents and redox potentials simultaneously with a novel redox potential-sensitive electrode. The H2O2-mediated KCa current increase was accompanied by a whole-cell redox potential decrease.


CONCLUSIONS
H2O2 elicited both hyperpolarization and depolarization of the membrane potential through 2 different mechanisms. Low H2O2 concentrations inhibited inward-rectifying K+ currents, whereas higher H2O2 concentrations increased the amplitude of the outward K+ current. We suggest that reactive oxygen species generated locally increases the KCa current amplitude, whereas low H2O2 concentrations inhibit KIR via intracellular messengers.
Bychkov
R
R
Franz Volhard Clinic and Max Delbrück Center for Molecular Medicine, Medical Faculty of the Charité, Humboldt University of Berlin, Berlin, Germany.
Pieper
K
K
Ried
C
C
Milosheva
M
M
Bychkov
E
E
Luft
F C
FC
Haller
H
H
D002118:Calcium / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D016877:Oxidants / Q000494:pharmacology*; D010084:Oxidation-Reduction; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D013482:Superoxide Dismutase / Q000494:pharmacology
D016166:Free Radical Scavengers; D016877:Oxidants; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D002118:Calcium