Shensong Yangxin blocks multiple cardiac ion channels in isolated ventricular myocytes, providing a potential mechanistic basis for its antiarrhythmic properties.
Background Shensong Yangxin (SSYX) is one of the compound recipe of Chinese materia medica. This study was conducted to investigate the effects of SSYX on sodium current (INa), L-type calcium current (ICa,L), transient outward potassium current (Ito), delayed rectifier current (IK), and inward rectifier potassium currents (IK1) in isolated ventricular myocytes. Methods Whole cell patch-clamp technique was used to study ion channel currents in enzymatically isolated guinea pig or rat ventricular myocytes. Results SSYX decreased peak INa by (44.84±7.65)% from 27.21±5.35 to 14.88±2.75 pA/pF (n=5, P<0.05). The medicine significantly inhibited the ICa,L. At concentrations of 0.25, 0.50, and 1.00 g/100 ml, the peak ICa,L was reduced by (19.22±1.10)%, (44.82±6.50)% and (50.69±5.64)%, respectively (n=5, all P<0.05). SSYX lifted the I-V curve of both INa and ICa,L without changing the threshold, peak and reversal potentials. At the concentration of 0.5%, the drug blocked the transient component of Ito by 50.60% at membrane voltage of 60 mV and negatively shifted the inactive curve and delayed the recovery from channel inactivation. The tail current density of IK was decreased by (30.77±1.11)% (n=5, P<0.05) at membrane voltage of 50 mV after exposure to the medicine and the time-dependent activity of IK was also inhibited. Similar to the effect on IK, the SSYX inhibited IK1 by 33.10% at the test potential of-100 mV with little effect on reversal potential and the rectification property. Conclusions The experiments revealed that SSYX could block multiple ion channels such as INaICa,L, IK, Ito and IK1, which may change the action potential duration and contribute to some of its antiarrhythmic effects. Chin Med J 2007;120(12):1068–1074
Li et al. (Fri,) studied this question.