Fig 2.

Properties of cellular cardiac Ca²⁺ buffers. A (i) Steady state Ca²⁺ buffering showing the dependence of bound on free Ca²⁺. The coloured curves show the contributions of the two Ca²⁺ binding sites (regulatory and Mg) of TnC, myosin and SERCA. The solid black line shows the total, calculated as the sum of these components and the others listed in Table 1. The dotted black line represents the sum of the fast buffers (top part of Table 1). (ii) Buffer power (calculated as in equation 2) as a function of [Ca²⁺]_i. B. Time course of change of bound [Ca²⁺] in response to systolic Ca²⁺ transients applied at 1.5 Hz. (i) Absolute levels of [Ca²⁺]. The dashed line shows free [Ca²⁺] and the coloured traces the concentration of the Ca²⁺-bound form of the various ligands. (ii) normalized concentrations to emphasise kinetics. C. The change of bound Ca²⁺ in response to a series of Ca²⁺ transients (not shown) applied at 1.5 Hz.