Fig. 4.

Effect of 4-min perfusion with Tyrode solution containing 211 μM EGTA AM on Ca²⁺ dynamics in the SR lumen measured with mag-fluo-4 AM (A–C). Measurements were conducted at 37°C at a pacing frequency of 4 Hz. A: representative traces obtained before (thin line) and 4 min after (thick line) perfusion with EGTA AM. B and C: changes in the diastolic (resting) and systolic (nadir) levels of mag-fluo-4 fluorescence (B) and decline in the amplitude of Ca²⁺ depletion (C) in response to 4-min treatment with 211 μM EGTA AM. The period of treatment with EGTA AM is indicated by the shaded bar. Data are means ± SD; N is the number of independent experiments (hearts). P values are the results of one-way ANOVA (initial vs. final levels of the parameters). D: typical traces of fluorescence from mouse hearts loaded with mag-fluo-4 AM in the absence (thin line) and presence (thick line) of 211 μM EGTA AM (37°C, 2 Hz). Traces were normalized to the maximum amplitude of the depletion to compare the kinetics.