Aim: To study the effect of puerarin (Pue) on Na+ channel in rat ventricular myocytes.
Methods: Whole-cell patch-clamp technique was applied on isolated cardiomyocytes from rats.
Results: Pue inhibited cardiac INa in a positive rate-dependent and dose-dependent manner, with an IC(50) of 349 micromol/L. The kinetics of blockage of cardiac sodium channel by Pue resembled the ClassIa/Ic of antiarrhythmic agents. Pue 300 micromol/L did not alter the shape of the I-V curve of INa, but markedly shifted the steady-state inactivation curve of INa towards more negative potential by 15.9 mV, and postponed the recovery of INa inactivation state from (21.9+/-1.6) ms to (54.4+/-3.4) ms (P<0.01). It demonstrated that the steady state of inactivation was affected by Pue significantly.
Conclusion: Pue protected ventricular myocytes against cardiac damage and arrhythmias by inhibiting recovery from inactivation of cardiac Na+ channels.