Fig. 6

Effect of the L-type Ca²⁺ channel activator Bay K8644 on cardiac Ca²⁺ levels and ventricular shortening of 3 and 5 dpf zebrafish larvae. Tg(myl7:Twitch-4) larvae at 3 (n = 13, N = 3) and 5 dpf (n = 10, N = 3) were treated with 100 µM Bay K8644. (A) Emission ratio images of a ventricular systole of representative larvae before (basal) and after 10 min incubation with Bay K8644. The traces show their atrial (red) and ventricular (black) Ca²⁺ levels (emission ratio). (B) Effect of Bay K8644 on the average Ca²⁺ levels and Ca²⁺ transient amplitude in the atrium and ventricle. Data are shown as the mean (black line) ± SD (gray stripe). (C) Diagrams of the ventricular vs. atrial Ca²⁺ levels (one cardiac cycle) of representative larvae before (basal) and after 10 min incubation with Bay K8644. (D) Diagrams of the ventricular diameter vs. ventricular Ca²⁺ level (one cardiac cycle) of representative larvae before (basal) and after 10 min incubation with Bay K8644. The plot shows the fold change over the basal FS of larvae treated with Bay K8644 for 10 min. A two-tailed unpaired Student's t-test was used (*** p < 0.001).