Fig. 4.

Basal SR Ca²⁺-load assessed by fast caffeine exposure is reduced in TG cells. a Representative traces illustrating [Ca²⁺]_i transients measured in response to 10 mM caffeine in WT (black) and TG (red) cells. The fluorescence signals were measured with fura-2AM in cells paced at 0.5 Hz. b Quantification of [Ca²⁺]_i transient amplitudes expressed as ratiometric fluorescence signals (ΔR = F₃₄₀/F₃₈₀) under basal conditions. c Mono-exponential constant of the Ca²⁺ transient decay (WT = 68 cells, 6 hearts; TG = 56 cells, 6 hearts); values are mean ± SEM based on numbers of cells; *p < 0.05