Model simulated effects of MCU Ca²⁺ uptake pool on [Ca²⁺]_i and [Ca²⁺]_m under control (A and C) and NKA inhibition (B and D) conditions during the transition of increasing pacing (from 0.25 Hz to 2 Hz).

<p>Different colors represent different p1:p2 ratios: red (1∶0); green (3∶1); black (1∶1); blue (1∶3); and pink (0∶1). (E). Summarized effect of p1:p2 ratio on [Ca²⁺]_m accumulation in response to increased energy demand. (F) Experimental data of the effect of NKA inhibition on [Ca²⁺]_m accumulation (Reproduced from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093928#pone.0093928-Liu1" target="_blank">[1]</a> with permission). The pacing frequency was increased to 1 Hz at 60 s.