FIGURE 3. Inhibition of PQ²⁺-induced H₂O₂ production in stimulated mitochondria.

Fluorometric (a) measurement of H₂O₂ production from isolated mitochondria in the presence of succinate was measured in the presence of PQ²⁺(250 μM, □), antimycin A (◆), antimycin A and PQ²⁺(◇), PQ²⁺ and SOD (▲), and PQ²⁺and catalase (△). Polarographic (b) measurement was used to confirm results. Following the addition of 250 μM PQ²⁺, H₂O₂ production in mitochondria was monitored with inhibitors added as indicated: rote-none (solid line), catalase (dotted line), and antimycin A (dashed line). Rates of H₂O₂ production before and after the addition of inhibitor (steady state 1 and 2, respectively) were compared with obtain the percentage of H₂O₂ production under each condition (see Fig. 5).