Comparison of outward current inactivation properties in male and female wild-type myocytes.

<p>For the compound outward current in male and female wild-type (KChIP2^+/+) myocytes the kinetics of macroscopic inactivation, the kinetics of recovery from inactivation and the voltage dependence of inactivation were compared. Data from male myocytes are depicted as black symbols, data from female myocytes as empty symbols. <b>A.</b> Representative outward current traces from a male and a female KChIP2^+/+ myocyte, respectively, recorded during a 5 s voltage pulse to +40 mV (voltage protocol shown below current traces; dotted line represents non-inactivating current level). For both sexes KChIP2^+/+ outward current decay kinetics were best described by a triple-exponential function. Note the slightly faster decay kinetics in the female myocyte. <b>B.</b> Mean time constants obtained with a triple-exponential function (τ1, τ2 and τ3). <b>C.</b> Mean amplitudes of the individual time constants obtained by triple-exponential fitting (A1, A2 and A3) and the amplitude of the non-inactivating current component (A0). <b>D.</b> Mean total amplitude of the compound outward current (AΣ). <b>E.</b> Recovery data fitted by a double-exponential function. Note that for female KChIP2^+/+ myocytes the recovery from inactivation was apparently faster. <b>F.</b> Mean recovery time constants (τ_rec1 and τ_rec2) obtained by double-exponential fitting. <b>G.</b> Data describing the voltage dependence of inactivation fitted with the sum of two Boltzmann-functions. Note the apparent negative shift of the fitting curve in female relative to male KChIP2^+/+ myocytes. <b>H.</b> Mean values for V_1/21 and V_1/22 obtained with the sum of two Boltzmann-functions (¶, unpaired Student’s <i>t</i>-test).