LCR activity and background Ca at low and high SR Ca pumping rate Pup of 4 mM/s and 24 mM/s as membrane depolarizes from the MDP (Maximal Diastolic Potential) to -50 mV (a threshold of I_CaL activation).

<p>(A): Local Ca distribution in submembrane cytosol voxels at the scale of 5 μM. The LCR activity increases during diastolic depolarization, but remains much lower at lower Pup. The background Ca does not appear different at this large Ca scale. (B) The same Ca distribution at a smaller scale of 0.25 μM. At low Pup, the cytosol is not efficiently cleared of Ca by the Ca pump after action potential-induced Ca transient and Ca distribution at the MDP (sub-panel a) shows substantially higher background and multiple small LCRs. Conversely, higher SR Ca pumping rate of 24 mM/s efficiently clears cytosol of Ca and the background Ca decreases (black background in sub-panel c). See also <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1005675#pcbi.1005675.s001" target="_blank">S1</a> and <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1005675#pcbi.1005675.s002" target="_blank">S2</a> Movies for more details and dynamic representation of the numerical model simulation results.