Suxiao Jiuxin Pills, a Chinese herbal complex, block human potassium channel current hKv1.5 in CHO cells

Kv1.5 channel plays key roles in cardiac action potential and atrial repolarization. Suxiao Jiuxin Pills (SXJ), an herbal remedy had been widely used in China in treating angina pectoris and atrial arrhythmia. However, whether SXJ regulates Kv1.5 channels is still unclear. The goal of the present study was to examine the effects of SXJ on cloned human potassium channels (hKv1.5) in Chinese hamster ovary (CHO) cells. The ionic and gating currents were detected; dose-dependent curve, current-voltage curve, steady-state activation curve (SSA), activation time constant (τ act ), deactivation (τ deact ), and gating currents were compared between SXJ and control. Further, intracellular application of SXJ was implemented. Results showed that SXJ inhibited the hKv1.5 current in a time-, dose- and voltage-dependent manner with a half maximal inhibitive concentration (IC 50 ) value of 38.85 milligram per liter. The voltage dependence was described by an equivalent electrical distance δ of 0.15, which suggested that at the binding site SXJ experienced 15% of the applied transmembrane electrical field. There were no significant different changes of SSA, τ act , τ deact , ‘On’ gating current (on- I g ), and ‘off’ gating current (off- I g ) between SXJ and Control ( P >  0.05). Intracellular application of SXJ could block the hKv1.5 current significantly ( P <  0.05). In conclusion, SXJ produces a dose-, time-, and voltage-dependent block of hKv1.5, with interacting electrical distance δ of 0.15. SXJ did not influence the gating currents and deactivation time course. SXJ was an open-blocker, which provided the experimental research of SXJ in clinical treating atrial arrhythmia.