Impact of treatment with Tripterygium wilfordii Hook F on proteinuria in NZB/W F1 mice. Proteinuria was determined by spectrophotometry as described in Materials and methods. Data are the means ± standard error of the mean of each group. Numbers in parentheses indicate the animals examined. (a) Changes in proteinuria in NZB/WF1 mice during the treatment course. Statistical analysis was done for proteinuria measured before and at each time point after treatment for each group. Proteinuria increased significantly in the mice of the vehicle group (*p < 0.05; ***p < 0.001; ****p < 0.0001; before treatment verses after treatment). (b) Proteinuria was compared between groups before and after treatment. No significant difference was determined before treatment between the three groups. After treatment, proteinuria was significantly higher in the vehicle treated mice than in mice treated with the ethyl acetate (EA) extract (**p < 0.0026, EAlow versus vehicle; ****p < 0.0001, EAhigh versus vehicle).