Fig. 6.

Sarcoplasmic reticulum (SR) load is elevated in Rad^−/−. A: representative paced and caffeine-stimulated Ca²⁺ transients from WT and Rad^−/−. B and C: caffeine-induced Ca²⁺-release amplitude (B) and the ratio of stimulated calcium release to total caffeine-induced SR Ca²⁺ release (C) was greater in Rad^−/− compared with WT. D: caffeine decay constant (tau, τ) is significantly prolonged in Ca²⁺-free media. E: spark frequency is increased in Rad^−/− compared with WT. F: representative line scan showing stimulus (arrowhead) and sparks measured after a >e-fold decay of the global Ca²⁺ transient in WT and Rad^−/−; n = 3 mice per genotype. *P < 0.05, ***P < 0.001 vs. WT.