Inhibitory effects of berberine on IK1, IK, and HERG channels of cardiac myocytes.

ABSTRACT

AIM: To study the effects of berberine on inward rectifier potassium current (IK1) and outward delayed rectifier potassium current (IK) of guinea pig ventricular myocytes, and on human ether-a-go-go related gene (HERG) channel expressed in Xenopus oocytes. METHODS: Whole cell patch-clamp and geneclamp techniques were used to record ionic currents. RESULTS: Berberine prolonged action potential duration (APD) and inhibited IK1 and IK in a concentration-dependent manner. Berberine 100 micromol/L increased APD90 from (450 +\- 48) ms to (888 +\- 90) ms (n = 6, P < 0.01), and inhibited IK1 by 65 % +\- 7 % (n = 6, P < 0.01). Berberine 50 micromol/L inhibited IK by 57 % +\- 6 %, IKtail by 53 % +\- 6 % (n = 6, P < 0.01). Berberine produced a voltage-dependent block on IK that increased with stronger depolarization, and once all channels were activated, there was no further block at positive potentials. Berberine blocked the HERG channels potently with an IC50 value of approximately 75 micromol/L. This block was voltage-dependent, suggesting that it probably bind to either open or inactivated HERG channels. CONCLUSION: Berberine prolonged APD and possessed blocking effect on IK1, IK, and HERG channel expressed in Xenopus oocytes. The antiarrhythmic mechanism of berberine is related to its inhibitory effects on IK1, IK, and HERG channel.