FIGURE 5.

Quantitative assessment of mitochondrial contribution on Ca²⁺ removal during voltage-induced Ca²⁺ release. A, dynamic changes of cytosolic [Ca²⁺] derived from fluorescence changes in the region with normally polarized mitochondria (red trace), and in the region with depolarized mitochondria (black trace) using the method described in Ref. 30. B, Ca²⁺ release fluxes derived from Ca²⁺ transients as shown in A by applying the removal method (34). The parameters used are k_off-fluo-4 = 0.09 ms⁻¹, k_on-egta = 0.015 (μm,ms)⁻¹, k_off-egta = 0.0075 ms⁻¹, and SR pump rate k_uptake = 11 ms (32–34). Mitochondrial Ca²⁺ uptake flux (green trace in B) was derived by calculating the difference of fluxes between defective and normal regions. C, comparing the kinetics of increased cytosolic Ca²⁺ transient (Δ[Ca²⁺]_cyto, black trace) in the defective region and the mitochondrial Ca²⁺ change ([Ca²⁺]_mito, red trace) in the normal fiber region. [Ca²⁺]_mito was calculated by applying the modified method (35). Note the similar time course of those two.