Figure 6. Comparison of kinetic parameters for I_K,ur between CTL and ORC ventricular myocytes.

A, superimposed current records showing voltage dependence of steady-state inactivation for I_K,ur in CTL and ORC myocytes. The cells were held at various test potentials varying from −110 to −20 mV for 5 s. A 2.5 s voltage step to +30 mV preceded by an inactivating prepulse (at −40 mV for 100 ms) was then applied to measure the remaining current. B, graph comparing the voltage dependence of steady-state inactivation of I_K,ur between CTL and ORC mice. I/I_max is the current normalized to the current obtained with the −110 mV voltage step. Smooth lines are best-fit Boltzmann functions. C, family of current recordings showing the time course of recovery from inactivation for I_K,ur in CTL and ORC cells. Two voltage steps (+30 mV; P₁ = 1500 ms, P₂ = 500 ms) separated by 50, 100, 150, 200, 250, 500, 750, 1000, 2000 and 3000 ms were applied. Both steps were preceded by the I_to inactivating prepulse. D, graph comparing reactivation of I_K,ur between CTL and ORC myocytes. P₂/P₁ represents the ratio of the amplitude of the current generated by each pulse.