Fig. 3.

A. Sample traces of time-dependent changes in dityrosine (diTyr) fluorescence (excitation λ322 nm; emission λ422 nm) as an indicator of ONOO⁻ production in guinea pig isolated cardiac mitochondria stressed with CaCl₂ + succinate. Mitochondria (0.5 mg/mL) were suspended in buffer E containing 0.5 mM L-tyrosine (buffer D) in the presence of CaCl₂ (75 μM added at 90 s; with 40 μM EGTA), Na-succinate (10 mM added at 140 s), and the redox cycler menadione (10 μM added at 250 s). NOS inhibitors L-NAME and L-NNA (10 mM), the SOD mimetic TEMPOL (2.5 and 10 mM), and the global NO^• scavenger PTIO (100 μM and 500 μM), were added to the buffer before the addition of mitochondria. B. Summary of the mean (±SEM) baseline ONOO⁻ concentrations after treatments but before (at 60 s) CaCl₂+succinate or addition of menadione. The presence of drugs added to the buffer before adding mitochondria reduced baseline [ONOO⁻] compared to Control (no treatment). [ONOO⁻] was calibrated over a range of 1–300 μM (y = 92.965x − 270.2; R² = 0.98). For all treatments n=6 guinea pig hearts. For treatments vs. no treatment (Control): * P < 0.05; ** P < 0.005; *** P < 0.001.