IK1 in wt and dystrophic ventricular cardiomyocytes. (A) Typical original potassium current traces of a wt, mdx, and mdx-utr cardiomyocyte elicited from a holding potential of −100 mV by 500-ms steps to various voltages (the pulse protocol is shown in the inset of Fig. 1B). The dashed line indicates the zero current level. (B) Current density-voltage relationships derived from a series of experiments as shown in Fig. 1A (n = 38 for wt, 36 for mdx, and 13 for mdx-utr, respectively). The current levels at the end of the test pulse were evaluated and plotted against the applied voltages. The lines through the data points represent fits with the function: y = Y0/(1 + exp((x-V05)/k)). (C) Current density values at −100 mV (means ± SEM) are compared between wt and dystrophic (mdx and mdx-utr) cardiomyocytes. *** indicates that ANOVA revealed a highly significant difference between the tested groups (p < 0.001). (D) Current density values at −100 mV of wt and dystrophic cardiomyocytes from all experiments on female (♀) mice (n = 14 for wt, 15 for mdx, and 13 for mdx-utr). ** p < 0.01, ANOVA. E: Current density values at −100 mV of wt and mdx cardiomyocytes from all experiments on male (♂) mice (n = 24 for wt and 21 for mdx). * p < 0.05 (p = 0.011), Student's t-test.