IK1 and Kir2.1 mRNA and protein levels in control, DHF, and CRT. A, Representative current traces in lateral myocytes isolated from control, DHF, and CRT canine ventricles elicited by the diagrammed voltage-clamp protocol (holding potential -40 mV, test pulse 500 ms in duration). B, Steady state current-voltage (I-V) relationship of IK1 and outward current portion of the I-V (right) in each group. The voltage-clamp protocol is shown in the inset. C, IK1 density at -140 and -70 mV in anterior (ANT) and lateral (LTR) myocytes of each group. D and E, Kir2.1 mRNA and protein expression in anterior and lateral myocytes of each group. A or ANT indicates anterior; L or LTR, lateral; and CSQ, calsequestrin. †P<0.05 vs control; #P<0.05 vs DHF. The values in parentheses are the number of cells or tissue samples studied in this and all remaining figures.