Fig. 1

The relation between fluo-3 concentration and [Ca · Fluo-3] in the presence or absence of 50 mM caffeine. After Ca²⁺ loading, Ca²⁺ was released from the SR into a glass capillary lumen by rapid cooling (a) or 50 mM caffeine (b). G0M1.5F and G0RM0CafF solutions (see Table 1) were used for a and b, respectively, at 3°C. The fluorescence signal was measured with five different concentrations of fluo-3 and was calibrated in terms of Δ[Fluo-3-Ca] (see Eq. 1 in text). Each symbol represents mean ± SEM (n = 5)