Figure 1. Aconitase activity, H₂O₂ production, mitochondrial Fe²⁺ and cell viability in PQ²⁺ treated primary midbrain cultures.

(A) Primary midbrain cells were treated with 0, 250 and 500 µM PQ²⁺ for 3 hrs and aconitase and fumarase activities were measured spectrophotometrically. Data are expressed as units/grams of protein, bars represent mean±SEM, *p<0.05, one-way ANOVA (n = 3–4). (B) Primary midbrain cultures were incubated with 0, 250, 500 and 1000 µM PQ²⁺. H₂O₂ production was measured by amplex red after 2, 4 and 6 hrs. Data are expressed as % control; asterisks indicate a difference from vehicle treated control at each time point. Bars represent mean±SEM, *p<0.05, **p<0.001, two-way ANOVA (n = 12). (C) Mitochondrial Fe²⁺ was measured by RPA fluorescence. Mean pixel intensity of 3 random fields/well was quantified using Image J (NIH) and expressed as % control. Asterisks indicate difference from vehicle treated controls. Bars represent mean±SEM, *p<0.05, **p<0.01, one-way ANOVA (n = 6). (D) Cell viability was assessed spectrophotometrically using MTT after 18 hrs of PQ²⁺ incubation. Each point represents mean±SEM (n = 5).