Fig. 6.

Chronic rotenone treatment increased apoptotic cell death before and after H₂O₂ exposure. Cells were analyzed for DNA fragmentation using TUNEL staining before and 24 hr after H₂O₂ exposure. Control cells showed little evidence of apoptosis (A), whereas cells treated with rotenone for 4 weeks showed a small but significant increase in apoptosis before H₂O₂ exposure (C, E). Cultures treated with rotenone for 4 weeks showed more TUNEL-positive cells after H₂O₂exposure (D) compared with control cultures (B). Arrows indicate some TUNEL-positive cells. E, Quantification of apoptotic cells. Cultures treated with rotenone for 4 weeks showed elevated apoptosis before and 24 hr after H₂O₂ exposure. Results are expressed as mean ± SEM of four experiments. *p < 0.05 compared with control.