Effects of equol on multiple K(+) channels stably expressed in HEK 293 cells

The present study investigated the effects of equol on cardiovascular K(+) channel currents. The cardiovascular K(+) channel currents were determined in HEK 293 cells stably expressing cloned differential cardiovascular K(+) channels with conventional whole-cell patch voltage-clamp technique. We found that equol inhibited hKv1.5 (IC(50): 15.3 μM), hKv4.3 (IC(50): 29.2 μM and 11.9 μM for hKv4.3 peak current and charge area, respectively), I(Ks) (IC(50): 24.7 μM) and I(hERG) (IC(50): 31.6 and 56.5 μM for I(hERG.tail) and I(hERG.step), respectively), but not hKir2.1 current, in a concentration-dependent manner. Interestingly, equol increased BK(Ca) current with an EC(50) of 0.1 μM. It had no significant effect on guinea pig ventricular action potentials at concentrations of ≤3 μM. These results demonstrate that equol inhibits several cardiac K(+) currents at relatively high concentrations, whereas it increases BK(Ca) current at very low concentrations, suggesting that equol is a safe drug candidate for treating patients with cerebral vascular disorders.