Effect of I3S on nuclear receptor activation. COS-1 cells were transfected with 25 ng of CMV2-CAR or CMV2-PXR expression plasmid, 25 ng 3.1-RXRα expression plasmid, 100 ng of luciferase reporter, and 10 ng of pRL-CMV. After 18 h, cells were treated as indicated and each treatment was performed in quadruplicate. At 24 h post-treatment, the cells were lysed and analyzed for luciferase activity. All values represent the mean ± standard deviation. The double asterisk indicates significant difference (p<0.05) compared with androstanol control values and the single asterisk indicates significant difference (p<0.05) compared with carrier solvent control values.