Fig. 2. Effects of H₂O₂ on HUVEC cell growth. Cells were seeded at a density of 7000 cells/well and then treated with 100, 200, 300, 400, 500, 600, 700, and 800 μmol/L H₂O₂ for 1 h (a) or 3 h (b). The control group was treated with RPMI-1640. Cell viability was then determined by MTT assay. Data are presented as mean±standard deviation (SD) with three independent experiments. ^** P<0.01, ^*** P<0.001, compared with the control.