(a)
(b)
Figure 2: Metabolic activity, measured by MTT assay, of NB4 cells treated with esculetin alone or combined with oxidants. (a) Metabolic activity of NB4 cells treated with esculetin and H2O2. Cells (5 × 105/ml) were exposed to 100 M esculetin, 1 mM H2O2, or both, for different times. (b) Metabolic activity of NB4 cells treated with esculetin and t-BHP. Cells (5 × 105/ml) were exposed to 100 M esculetin or 100, 250, and 500 µM t-BHP separately or in combination, for the indicated times. Data are expressed as mean ± SEM of four independent experiments. Treated versus untreated cells; . Treated with esculetin plus oxidant versus esculetin alone; . Treated with esculetin plus oxidant versus oxidant alone; .