Fig. 6.

A: diastolic SR RyR Ca²⁺ leak in normal HEPES 1.8 mmol/l Ca²⁺ solution in sedentary and exercise-trained transgenic (TG) CaMKIIδ_C-overexpressing mice and WT mice. B: RyR Ca²⁺ leak after incubation by AIP (to inhibit CaMKII) and H-89 (to inhibit PKA) in sedentary TG mice. Note that exercise training reduced the Ca²⁺ leak to levels found in WT mice and inhibiting CaMKII with AIP abolished Ca²⁺ leak. PKA inhibition by H-89 had no significant effect (NS) on reducing Ca²⁺ leak. No significant effects of H-89 or AIP were seen in any of the other groups. C: frequency of spontaneous Ca²⁺ waves was higher in sedentary TG compared with WT; exercise training reduced Ca²⁺ wave frequency to WT levels. Number of animals in each group for cardiomyocyte data N = 5, number of cells in each group n = 25–30. D: phosphorylation of serine-2814 residues at RyR2; example blots in inset (protein expressions are presented as means ± SE, number of rats in each group N = 4). **P < 0.01 vs. other groups, *P < 0.05 vs. other groups, #P < 0.05 between sedentary TG and sedentary WT.