Figure 3. Protective effect of vitamin C against 6.25 μM hydrogen peroxide–induced proliferation of orbital fibroblasts from patients with Graves’ ophthalmopathy. After pretreatment of Graves’ ophthalmopathy (GO) orbital fibroblasts (n=7) with 250 μM or 500 μM vitamin C (VitC) for 1 h, followed by the addition of 6.25 μM hydrogen peroxide (H₂O₂) for 24 h, the cell proliferation rate was examined with the AlamarBlue assay. The data were normalized to each control not exposed to H₂O₂, and the mean values of cell proliferation from GO orbital fibroblasts are shown in the histogram. The pretreatment of VitC at 250 μM and 500 μM in GO orbital fibroblasts significantly inhibited H₂O₂-induced cell proliferation. The data are presented as mean ± standard deviation of the results from three independent experiments. (p<0.005 and p<0.0001 represented significant decrease.)