Calcium interferes with titin-eGFP dynamics. (A) Images of embryonic cardiomyocytes (E13.5) maintained at low vs. high calcium levels (0.9 mM LCa vs. 2.8 mM HCa) were obtained before and immediately after bleaching (white arrows). 14 h after bleaching the titin-eGFP signal was recovered only partially in cells treated with high as compared with low calcium. Bar, 10 µm. (B) Recovery profile of the bleached region over time. The titin-eGFP mobility was significantly increased at low calcium concentration and decreased at high calcium concentration as compared with control cells (normal, NCa, 1.8 mM; n = 4). (C) Mobile fractions decreased with increasing levels of calcium (n = 4 per group). *, P < 0.05; **, P < 0.01; ***, P < 0.001. Error bars indicate SEM.