Figure 4. Effect of O2– on the evaluation of MC3T3-E1 cell proliferation by the WST-1 assay. MC3T3-E1 cells (4×104 cells/ml) were incubated at 37°C in 5% CO2 for 72 h. (A) White column represents the results of the WST-assay in untreated MC3T3-E1. The mean absorbance value of this assay was represented as 100 %. Black column represents the results of the WST-1assay in MC3T3-E1 cells treated with superoxide dismutase (SOD; 300 units/ml). Right columns represent the results of the assay in MC3T3-E1 cells cultured with SOD (300 units/ml). Values are mean±SE for 8 wells. (B) Phase contrast image of cultured MC3T3-E1 cells, showing undistinguishable morphology between a normal culture and the culture added with SOD.