Aim: To examine the effects of berberine, an isoquinoline alkaloid with a long history used as a tonic remedy for liver and heart, on ion channels of isolated rat hepatocytes.
Methods: Tight-seal whole-cell patch-clamp techniques were performed to investigate the effects of berberine on the delayed outward potassium currents (I(K)), inward rectifier potassium currents (I(K1)) and Ca(2+) release-activated Ca(2+) currents (I(CRAC)) in enzymatically isolated rat hepatocytes.
Results: Berberine 1-300 micromol/L reduced I(K) in a concentration-dependent manner with EC(50) of 38.86+/-5.37 micromol/L and n(H) of 0.82+/-0.05 (n = 8). When the bath solution was changed to tetraethylammonium (TEA) 8 mmol/L, I(K) was inhibited. Berberine 30 micromol/L reduced I(K) at all examined membrane potentials, especially at potentials positive to +60 mV (n = 8, P<0.05 or P<0.01 vs control). Berberine had mild inhibitory effects on I(K1) in rat hepatocytes. Berberine 1-300 micromol/L also inhibited I(CRAC) in a concentration-dependent fashion. The fitting parameters were EC(50) = 47.20+/-10.86 micromol/L, n(H) = 0.71+/-0.09 (n = 8). The peak value of I(CRAC) in the I-V relationship was decreased by berberine 30 micromol/L at potential negative to -80 mV (n = 8, P<0.05 vs control). But the reverse potential of I(CRAC) occurred at voltage 0 mV in all cells.
Conclusion: Berberine has inhibitory effects on potassium and calcium currents in isolated rat hepatocytes, which may be involved in hepatoprotection.