Isoliensinine (IL) extracted from lotus seed has a good therapeutic effect on cardiovascular diseases. However, its effect on ion channels of ventricular myocytes is still unclear. We used whole-cell patch-clamp techniques to detect the effects of IL on transmembrane ion currents and action potential (AP) in isolated rabbit left ventricular myocytes. IL inhibited the transient sodium current (INaT), late sodium current (INaL) enlarged by sea anemone toxin (ATX II) and L-type calcium current (ICaL) in a concentration-dependent manner without affecting inward rectifier potassium current (IK1) and delayed rectifier potassium current (IK). These inhibitory effects are mainly manifested as reduced the AP amplitude (APA) and maximum depolarization velocity (Vmax) and shortened the action potential duration (APD), but had no significant effect on the resting membrane potential (RMP). Moreover, IL significantly eliminated ATX II-induced early afterdepolarizations (EADs) and high extracellular calcium-induced delayed afterdepolarizations (DADs). These results revealed that IL effectively eliminated EADs and DADs through inhibiting INaL and ICaL in ventricular myocytes, which indicates it has potential antiarrhythmic action.
Keywords: Delayed afterdepolarizations; Early afterdepolarizations; Isoliensinine; L-type calcium current; Late sodium current.