Fig. 4
Delayed rectifier K+ currents expressed in P19CL6-derived cardiomyocytes and P19CL6-Csx-derived cardiomyocytes. Current–voltage relationships of E4031-sensitive currents (IKr) (a, b), and chromanol 293B-sensitive currents (IKs) (c, d). Each inset shows representative current traces (at 0 mV in IKr, at + 30 mV in IKs,) before (white up-pointing triangle) and after (black up-pointing triangle) application of each inhibitor. Scales of insets are 200 ms and 100 pA for IKr, 500 ms and 200 pA for IKs. IKr was elicited by 1 s-depolarizing pulses from a holding potential of ‒ 40 mV to the test potentials between ‒ 30 and + 40 mV (10 mV increments). IKs was elicited by the same protocol as IKr, except for the duration of depolarizing pulse (3 s). Current amplitude was measured at the end of the depolarizing test pulse and normalized by cell capacitance. *p < 0.05 compared with P19CL6 cells in the early stage