Fig. 6. Human SR-BI overexpression in HepG2 cells. HepG2 cells were stably transfected with a eukaryotic expression vector containing human SR-BI cDNA and clones were isolated. (A) SR-BI levels of normal HepG2 cells and of two overexpressing clones (S1.1 and S1.7) determined by immunoblotting with anti-SR-BI polyclonal antibody (1:5000) as described under Materials and Methods. Shown here is a representative image from five different protein extractions. (B) [³H]CE association (black bars) and ¹²⁵I-protein association (white bars) of LDL (n=9) and HDL₃ (n=9) in HepG2 cells overexpressing SR-BI measured as described in figure 3. (C) ¹²⁵I-M-BSA association (black bars) and recycling (retroendocytosis, white bars) (n=4) in HepG2 cells overexpressing SR-BI measured by incubating ¹²⁵I-M-BSA with cells at 20 µg/ml for 2 hours at 37°C according to the pulse-chase protocol described in Materials and Methods. Statistically different values from the control HepG2 cell values (or otherwise indicated) are indicated as: ^aP<0.05; ^bP<0.01 and ^cP<0.001.