Fig. 6.

Electrically stimulated and caffeine-induced intracellular Ca²⁺ transients in wt and Dmd^mdx rat ventricular cardiomyocytes. (A,B) Representative time courses of Fluo-4 fluorescence reporting rises in cytosolic Ca²⁺ concentration during electrical field stimulation, at 0.2 Hz frequency, in a single wt (A) and Dmd^mdx (B) myocyte. (C) Comparison of mean Ca²⁺ peak fluorescence relative to baseline (F/F0) between wt and Dmd^mdx myocytes. Each data point represents a single cell, and values are expressed as means±s.d. [n=67 and n=53 for wt (four animals) and Dmd^mdx (four animals) myocytes, respectively]. (D) Comparison of the Ca²⁺ transient decay kinetics in wt and Dmd^mdx cardiomyocytes. The decay of the electrically induced Ca²⁺ signal following the rapid initial rise was fitted with a single exponential function to derive τ-values. (E,F) Time courses of Fluo-4 fluorescence reporting rises in cytosolic Ca²⁺ concentration during application of 20 mM caffeine in a wt (E) and Dmd^mdx (F) myocyte. The gray bars indicate the time period of superfusion with bath solution containing caffeine. (G) Comparison of mean Ca²⁺ peak fluorescence, elicited by caffeine application, relative to baseline (F/F0) between wt and Dmd^mdx myocytes [n=40 and n=39 for wt (four animals) and Dmd^mdx (four animals) myocytes, respectively]. (H) Comparison of the Ca²⁺ transient decay kinetics (expressed as τ-values) during caffeine application in wt and Dmd^mdx cardiomyocytes. *P<0.05, ***P<0.001, unpaired Student's t-test.