Figure 3.

MCU strength on intracellular Ca²⁺ cycling. The maximal MCU activity was increased to a higher level after the cell was paced into the steady state (20 beats). The total number of simulated beats for each case is 50, and the PCL is 2 s. From left to right, time courses of ${\overline{\left[C{a}^{2+}\right]}}_m$, ${\overline{\left[C{a}^{2+}\right]}}_i$, and ${\overline{\left[C{a}^{2+}\right]}}_{JSR}$are shown. (A) MCU faces the cytosolic space. (B) MCU faces the submembrane space. (C) MCU faces the dyadic space. (D) Bar plots summarize the peak values of ${\overline{\left[C{a}^{2+}\right]}}_m$ (left), ${\overline{\left[C{a}^{2+}\right]}}_i$ (middle), and ${\overline{\left[C{a}^{2+}\right]}}_{JSR}$ (right) at the 50th beat for different MCU localizations and different maximal MCU activity. To see this figure in color, go online.