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Background. Licorice has long been used to treat many ailments including cardiovascular disorders in China. Recent studies have shown that the cardiac actions of licorice can be attributed to its active component, glycyrrhetinic acid (GA). However, the mechanism of action remains poorly understood. Aim. The effects of GA on the delayed rectifier potassium current (I K), the rapidly activating (I Kr) and slowly activating (I Ks) components of I K, and the HERG K+ channel expressed in HEK-293 cells were investigated. Materials and Methods. Single ventricular myocytes were isolated from guinea pig myocardium using enzymolysis. The wild type HERG gene was stably expressed in HEK293 cells. Whole-cell patch clamping was used to record I K (I Kr, I Ks) and the HERG K+ current. Results. GA (1, 5, and 10 μM) inhibited I K (I Kr, I Ks) and the HERG K+ current in a concentration-dependent manner. Conclusion. GA significantly inhibited the potassium currents in a dose- and voltage-dependent manner, suggesting that it exerts its antiarrhythmic action through the prolongation of APD and ERP owing to the inhibition of I K (I Kr, I Ks) and HERG K+ channel.

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To investigate the effects and mechanisms of total flavones of Epimedium (TFE) on oxidative stress induced by myocardial ischemia/reperfusion injury in rats, forty male SD rats were randomly divided into sham operated group, model group, diltiazem group and flavonoids of Epimedium low and high doses groups with 8 rats in each. Myocardial ischemia/reperfusion injury model was induced by ligaturing the left anterior descending artery for 30 min followed reperfusion for 4 h after TFE was taken by intragastric administration for 4 days. The degree of myocardial infarct was observed by N-BT staining. The concentrations of MDA and activities of SOD and T-AOC in cardiac tissue were measured by colorimetry. Serum TnI concentrations were checked by ELISA. HE stain was used to observe myocardium structure under light microscope. Expressions of SIRT1 and Nrf2 in cardiac tissue were evaluated by immunohistochemistry method and Western blot, respectively. Compared with the model group, the degree of myocardial infarct, MDA concentration in cardiac tissue and the levels of TnI in serum significantly decreased in the diltiazem group and flavonoids of Epimedium low and high doses groups (P<0.05 or P<0.01); flavonoids of Epimedium low and high doses groups and the diltiazem group also showed improvements in myocardium structure under ischemia/reperfusion injury. TFE significantly increased the activity of SOD and T-AOC and the expression of SIRT1 and Nrf2 in cardiac tissue when compared with the model group (P<0.05 or P<0.01). Therefore, TFE can increase anti-peroxidant capacity of myocardium tissue by using intrinsically anti-oxidant signaling pathway of SIRT1 and Nrf2, which can inhibit irreversible damage of cardiomyocytes in myocardial ischemia/reperfusion injury and protect normal function of cardiac tissue.