Figure 6.

Deficient EC coupling in SC35 knockout cardiomyocytes. (A) Typical confocal Ca²⁺ images of single isolated cardiomyocytes from wild-type or knockout mice. Cultured cells were loaded with fluo-4 followed by pacing at designated frequencies. Line-scan images are displayed with time and space on the abscissa and ordinate, respectively. (B) Traces of spatially averaged Ca²⁺ transients (top) and the corresponding cell shortenings (bottom, downward defections). (C) Frequency dependence of peak Ca²⁺ transient (ΔF/F₀, where F₀ refers to the fluo-4 signal at rest). (D) Frequency dependence of twitch amplitude (TA, presented as percent diastolic cell length). ^*P<0.05; ^**P<0.01 by Student's t-test. N=17–22 for each data point.