Electrophysiological effects of changrolin, an anti-arrhythmic agent derived from Dichroa febrifuga, on guinea-pig and rabbit heart cells.

1. The electrophysiological effects of changrolin (CRL), a Chinese anti-arrhythmic drug derived from a traditional antimalarial plant, were examined using the whole-cell patch-clamp method on single cells isolated from guinea-pig and rabbit hearts. 2. At a clinically relevant concentration of 50 mumol/L changrolin inhibited ICa by 19.3 +/- 6.0% and 17.3 +/- 2.6% in guinea-pig and rabbit ventricular cells, respectively. The voltage-dependent channel availability curve was not affected. The CRL effect was enhanced to a small extent during a repetitive stimulation at 2 Hz. 3. INa was resistant to CRL and the channel availability curve was also unaffected. A small use-dependent inhibition was observed only when the INa was elicited at 5 Hz in the presence of 300 mumol/L CRL. 4. At 50 mumol/L, CRL did not affect the time-independent inward rectifier and the delayed rectifier K+ currents (IK1 and IK, respectively), but inhibited the transient outward current (ITO) by 17.7 +/- 2.4%. Changrolin significantly shortened the action potential duration in both guinea-pig and rabbit ventricular cells. 5. In conclusion, CRL inhibits ICa and ITO but has little effect on INa.