SOD1 and Parkinson disease: As shown in Figure 3, when rats were treated with 6-OHDA, the activity of SOD and contents of GSH in the SN was 18 U/mg protein and 25 mg/g protein, respectively (SOD: sham group, 51.77 ± 6.08; PD group, 18.41 ± 0.94; P = 0.0001.