SOD activity and SOD1 protein expression in EA.hy926 cells following low-dose X-irradiation. (A) Relative SOD activity as analysed 24 h after irradiation by using a colorimetric activity assay. Data represent means ± SD (n = 3). *p < 0.05 vs. 0.3 Gy and 0.7 Gy treated cells. (B) Western immunoblots from total cellular proteins at 24 h after irradiation using antibodies against SOD1 and β-actin for loading control. Data are displayed as one representative out of three independent experiments. (C) Reduction of SOD1 protein expression normalized to β-actin control as determined by densitometric analysis using the ImageJ software package from two independent experiments including data from (B). *p < 0.05 vs. 0.3 Gy and 0.7 Gy irradiated cells.