Figure 2.

[³H]Ryanodine binding of RyR1 in the presence of increasing Ca²⁺concentrations with and without AMPPCP and caffeine. Specific [³H]ryanodine binding to RyR1 was determined in 0.5 M choline Cl, 20 mM imidazole, pH 7 with 2 nM [³H]ryanodine and the indicated Ca²⁺ in the absence or the presence of 2 mM AMPPCP and/or 5 mM caffeine. Data are the mean ± SE of four to seven experiments. ^#p < 0.05 compared with Ca²⁺ only by two-way ANOVA followed by Holm–Sidak method and ∗p < 0.05 by Student's t test. RyR1, ryanodine receptor type 1.