Figure 7. CDCL and SDCL increase Ca²⁺-induced Ca²⁺ release from cardiac SR vesicles and compete strongly with the A peptides and partly with C peptides when activating RyR2 channels in bilayers.

(A) Relative rates of Ca²⁺-induced Ca²⁺ release are shown as a function of peptide concentration. Average data are shown for peptide C_s (●; n=5); C_c (■; n=5); SDCL (◆; n=2) and CDCL (▲; n=2). (B)–(E) Competition between the recombinant II–III loops and A or C peptide for activation of RyR2. In each experiment, 1 μM peptide was added for 4 min, and then the channel was exposed to 10 nM, 100 nM or 1 μM of II–III loop for 4 min at each concentration. Channels were treated with A_c and CDCL (B) (n=5), C_c and CDCL (C) (n=4), A_s and SDCL (D) (n=4), C_s and SDCL (E) (n=4).