Membrane current in WT and DMD ^mdx muscle fibers. (A) Individual and corresponding mean (±SD) values for the capacitance (Cm in nanofarad, nF) of WT and DMD^mdx fibers (n = 29 fibers from seven WT animals and n = 27 fibers from seven DMD^mdx animals. P = 0.006, nested t test). Each bar and superimposed data points correspond to data from a same animal. The inset shows the mean membrane current transients at the onset and termination of a −20 mV pulse from −80 mV, from all tested WT and in DMD^mdx muscle fibers. The bottom graph shows values for the capacitance as a function of the estimated surface membrane area of each corresponding fiber. Straight lines correspond to the result of a linear fit in each group. (B) Individual and mean (±SD) absolute values for holding current (I_H) in WT and DMD^mdx fibers (n = 29 fibers from seven WT animals and n = 27 fibers from seven DMD^mdx animals. P = 0.42, nested t test, 95% CI for the difference between mean values: −1.35 to 3.00). Each bar and superimposed data points correspond to data from a same animal. (C) Corresponding individual and mean (±SD) values for the holding current normalized to the capacitance (P = 0.005, nested t test). (D) Individual and corresponding mean (±SD) absolute values for the steady change in membrane current (ΔI/20 mV) measured at the end of the −20 mV pulse (P = 0.85, nested t test, 95% CI for the difference between mean values: −0.73 to 0.61). (E) Corresponding individual and mean (±SD) values for the steady current, normalized to the capacitance (P = 0.02, nested t test). 95% CI, 95% confidence interval.