T-Tubule Proximity Modulates RyR Properties Figure 1. Effect of proximity of TTs to RyR on spontaneous Ca2+ sparks. A. Typical example of a line scan image during and after 1 Hz stimulation. After loading the SR with conditioning pulses from 270 to +10 mV at 1 Hz, stimulation was stopped and 15 seconds of diastole were recorded for Ca2+ sparks. Sparks were assigned to early (blue) and delayed (red) release areas corresponding to their position on the scan line. B. Spark frequency and morphology in early vs. delayed release areas in CTRL pigs (Npigs = 12, ncells = 41). * denotes P,0.05. doi:10.1371/journal.pone.0025100.g001 Figure 2. Effect of sarcolemmal fluxes on spark frequency and duration. A. Effect of NCX block by 5 mM nickel on spark frequency and duration in early (left) and delayed (right) release areas in CTRL cardiomyocytes (Npigs = 3, ncells = 7). B. Effect of ICaL block by 50 mM cadmium on spark frequency and duration in early (left) and delayed (right) release areas in CTRL cardiomyocytes (Npigs = 2, ncells = 9). * denotes P,0.05. doi:10.1371/journal.pone.0025100.g002 PLoS ONE | www.plosone.org 4 October 2011 | Volume 6 | Issue 10 | e25100