Figure 5.

Elevated [Na⁺]_i increases ROS production in normal myocytes. A similar protocol as in Figure 2 was performed, except that isoproterenol was washed in starting 40 seconds after the onset of pacing. Pipette solution was 5 or 15 mmol/L [Na⁺]_i as indicated. A and B, [Ca²⁺]_c and [Ca²⁺]_m were measured in normal myocytes (5 mmol/L [Na⁺]_i, n=15; 15 mmol/L [Na⁺]_i, n=20). A, Systolic [Ca²⁺]_m plotted against systolic [Ca²⁺]_c; B, diastolic [Ca²⁺]_m plotted against diastolic [Ca²⁺]_c; the numbers indicate the time (in minutes) after the start of the experiment. C and D, Net H₂O₂ formation was determined by CM-DCF in a separate set of cells (n=15/12). CM-DCF oxidation, indicating levels of H₂O₂, is given as F/F₀ (C) or ΔF/F₀ per minute (D). *P<0.05 for 5 vs 15 mmol/L [Na⁺]_i at minute 6 to 18 (1-way ANOVA).