The effects of different tocopherols on the LDL receptor binding activity, protein and mRNA of HepG2 cells. Cells were incubated for 24 h at 37°C in media containing the indicated concentrations of either α-tocopherol (●), δ-tocopherol (○) or γ-tocopherol (▲). The LDL receptor binding activity (A) was measured in triplicate using colloidal-gold LDL. The LDL receptor protein (B) was measured by western blotting and the LDL receptor mRNA (C) was measured using a PCR and western blotting technique as described in Methods and materials and the data was expressed as the percent difference from the values obtained with control cells not pretreated with α-tocopherol. The LDL receptor activity in control cells averaged 40 ± 5 ng LDL/mg cell protein, the LDL receptor protein in control cells averaged 0.85 ± 0.39 absorbance units and the amount of LDL receptor mRNA in control cells averaged 4.0 ± 0.5 × 10-5 copies/μg RNA.