Figure 4. Effects of NOC12 and S107 on [³H]ryanodine binding to RyR1.

(A) Dependence of [³H]ryanodine binding on NOC12 concentration. SR vesicles not treated with FK506 were incubated for 5 h at 24°C in 0.25 M KCl, 20 mM imidazole, pH 7.0, 7 µM free Ca²⁺, protease inhibitors and the indicated concentrations of NOC12 in the presence (•) and absence (○) of 44 µM S107. Data are the mean ± SEM of 4 experiments. *p<0.05 compared to vesicles without S107. (B) Dependence of [³H]ryanodine binding to RyR1 on S107 concentration. SR vesicles were incubated as in A in the absence (○) and presence of 50 µM NOC12 (•) and the indicated concentrations of S107. Data are the mean ± SEM of 4 experiments. *p<0.05 compared to vesicles with 50 µM NOC12 and without S107. (C) Specific [³H]ryanodine binding to SR vesicles containing (−FK506) and depleted (+FK506) of FKBP12. [³H]Ryanodine binding was determined in the presence of 50 µM NOC12 and the absence and presence of 44 µM S107. Data are the mean ± SEM of 8 experiments. *p<0.05 compared to vesicles treated with FK506 and incubated in the absence of S107, ^#p<0.05 compared to vesicles not treated with FK506 and incubated in the absence of S107.