Hydrogen Peroxide Modulates Electrophysiological Characteristics of Left Atrial Myocytes.

Background: Oxidative stress plays an important role in the pathophysiology of atrial fibrillation (AF). The hydrogen peroxide (H2O2) mainly underlies the cellular oxidative stress and free radicals. Left atrium (LA) is the most important AF substrate. However, the effects of H2O2 on the action potential (AP) and ionic currents in LA myocytes have not been fully elucidated.Methods: The whole-cell patch clamp was used to investigate the APs and ionic currents of L-type calcium current (l(subscript Ca-L)), transient outward currents (I(subscript to)), ultra -rapid delayed rectifier potassium current (l(subscript Kur)), delayed rectifier potassium currents (l(subscript K)), inward rectifier potassium current (I(subscript k1)), and sodium-calcium exchanger (NCX) before and after H2O2 (100 μM) in isolated rabbit LA myocytes.Results: H2O2 (100 μM) shortened by 50% (from 40 ± 7 to 21 ± 5 ms) and 90% the AP duration (from 95 ± 12 to 74 ± 11 ms) in LA myocytes (n = 9), but did not change the resting membrane potentials. The H2O2 (100 μM) decreased I(subscript to), but increased I(subscript Kur) and I(subscript K). H2O2 (100 μM) also reduced the I(subscript Ca-L) and the reverse mode NCX. However, H2O2 (100 μM) did not change I(subscript K1).Conclusions: H2O2 directly modulated the AP morphology and ionic currents in LA myocytes, which may contribute to the genesis of AF in oxidative stress.