FIGURE 8.

Graphical representation of the proportion of Ca²⁺ bound by the major cytoplasmic fast Ca²⁺ binding moieties at the peak of the intracellular Ca²⁺ transient at the three developmental ages. Note that TnC binds ∼57% of the Ca²⁺ at each age. The proportion of Ca²⁺ bound by the SR increases, and this is offset primarily by corresponding decreases in Ca²⁺ bound by calmodulin and ATP. Ca²⁺ binding to total sarcolemmal (SL) sites and to creatine phosphate (PCr) is small and has been combined in the figure.