Comparative effects of DFP and other iron chelators on aconitase activity and on its regeneration after iron depletion. (A) Aconitase activity (units are in nanomoles of NADPH per minute) in lysates of T-rex–untreated cells subjected for 16 hours to increasing concentrations of chelators in normal culture conditions: DFP (●), DFO (○), DFR (▴), and SIH (▵). Aconitase activity was significantly reduced by all chelators, except DFP (n = 4, P < .05, one-way ANOVA with Dunnett post-hoc test). (B) T-rex cells induced (Tet⁺) or not with tetracycline for 6 days were treated for 30 hours with 150 μM DFO, washed, and recultured for 3 hours in full medium with or without 50 μM of the chelators indicated. Cells were subsequently lysed, and lysates were subjected to spectrofluorimetric aconitase activity assay and to immunoblotting with antibodies against mitochondrial aconitase (inset). The Tet⁺ systems with no supplementation or with DFO supplementation were the only ones that showed no significant increase after recovery (n = 3, P < .05, 1-tailed paired t tests). (C) T-rex 293 cells (not induced) were not treated or treated overnight with 100 μM DFO (DFO) or DFP (DFP). Cells were subsequently lysed, and 50 μg cell lysates was subjected to SDS-PAGE and immunoblotting using antiactin (top panel) and antifrataxin (bottom panel) antibodies.