Ionic mechanism of the effects of hydrogen peroxide in rat ventricular myocytes
Abstract
1. Whole-cell and amphotericin-perforated patch-clamp techniques have been used to study the effects of hydrogen peroxide (H2O2) on action potentials and underlying ionic currents in single myocytes from the ventricles of adult rat hearts. 2. The results obtained differed markedly depending on the recording method utilized. Conventional whole-cell recordings, in which the myoplasm is dialysed with the contents of the pipette, failed to show any significant effects of H2O2 on the action potential or cell shortening. In contrast, when action potentials were recorded with the amphotericin-perforated patch method, H2O2 (50-200 microM) produced a marked prolongation of the action potential and an increase in cell shortening. 3. Voltage-clamp recordings with the amphotericin-perforated patch method showed that H2O2 caused no significant changes in either the Ca(2+)-independent transient outward K+ current (Ito) or the inwardly rectifying K+ current (IK1). 4. Application of tetrodotoxin (TTX; 8 x 10(-6) M), a Na+ channel blocker, largely inhibited the effects of H2O2 on the action potential. Moreover, anthopleurin A (4 x 10 (-7) M), which augments Na+ current (INa) by slowing its inactivation, mimicked the effects of H2O2 on the actio...Continue Reading
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