The role of cytoplasmic Ca²⁺ buffering power in Ca²⁺ wave initiation and propagation. (A) Concentration dependencies of buffer power of important Ca²⁺ chelators in the cytoplasm and their summed total. Buffer power is defined as the ratio of change in total [Ca²⁺] to free [Ca²⁺]. z-t line-scan images of Fluo-4 fluorescence during a Ca²⁺ release (B) with Ca²⁺ buffering by chelators shown in A using the same conditions as in Fig. 6 and (C) when buffer power follows the fictitious, weak concentration dependence shown by the black dashed line in A.