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AIM: To study the effects of palmatine, a known inhibitoron delayed rectifier potassium current and L-type calciumcurrent (ICa,L) in guinea pig ventricular myocytes, on thepotassium and calcium currents in isolated rat hepatocytes.METHODS: Tight-seal wh ole-cell patch-clamp techniqueswere performed to investigate the effects of palmatine onthe delayed outward potassium currents (IK), inward rectifierpotassium current (IK1) and Ca2+ release-activated Ca2+current (ICRAC) in enzymatically isolated rat hepatocytes.RESULTS: Palmatine 0.3-100 μM reduced IK in a concentationdependent manner with EC50of 41.62±10.11 μM and nH,0.48±0.07 (n=8). The effect of the drug was poorly reversibleafter washout. When the bath solution was changed totetraethylammonium (TEA) 8 mM, IK was inhibited.Palmatine 10 μM and 100 μM shifted the I-V curves of IKdownward, and the block of IK was voltage-independent.Palmatine 0.3-100 μM also inhibited ICRAC in a concentration-dependent manner. The fitting parameters were as follows:ECs0=51.19±15.18 μM, and nH=0.46+0.07 (n=8). The peakvalue of ICRAC in the I-V relationship was decreased bypalmatine 10 μM and 100 μM. But the reverse potential ofIcRAcoCcurred at Voltage=0 mV in all cells. Palmatine 0.3-100 μM failed to have any significant effect on either inwardor outward components of IK1 at any membrane potentialexamined.CONCLUSION: The inhibitory effects on IK and ICRAC couldbe one of the mechanisms that palmatine exerts protectiveeffect on hepatocytes.