Figure 2.

Very low endogenous expression of TRs in CV-1 and CHO cells induced very low basal activity on a DR4-CON-tk reporter. CHO (A) or CV-1 cells (B) were transiently transfected via lipofection with an empty expression vector (EV) or expression vectors containing TRα1 or TRβ1, a consensus DR4-CON-tk-luciferase reporter, and β-galactosidase control in hormone-depleted medium. After 24 hours in hormone-depleted medium, the cells were exposed to the indicated T₃ or T₄ concentrations. Cells were incubated an additional 24 hours before harvest, and lysates were analyzed for luciferase activity and β-galactosidase levels. Luciferase values were normalized against the β-galactosidase control for each sample. Error bars indicate SEMs for at least 3 biological replicate experiments.