FIG. 4.

Role of complex III in bipyridyl herbicide–induced H₂O₂ production in isolated mitochondria. (A) Scheme of electron flow through complex III. The sites of inhibition by antimycin A, myxothiazol, and stigmatellin are indicated. Electron leak can occur at either of the ubiquinone-binding sites (Q_o or Q_i) to reduce molecular oxygen and form O₂^·−. (B) Isolated rat brain mitochondria were supplemented with succinate in the presence of rotenone to direct electron flow through complex III. PQ, DQ, and BV were used to stimulate H₂O₂ production where indicated in the presence of vehicle/dimethyl sulfoxide (DMSO) or complex III inhibitors. Data expressed as mean + SEM, n = 3. Bars with different letters indicate statistical significance from one another (p < 0.05, one-way ANOVA with Tukey's posttest).