Figure 4.

Regulation of ABC1 gene expression. Immortalized normal and TD1 and TD2 Tangier fibroblasts were incubated in serum-free medium plus albumin (filled bars), with the addition of 8-Br-cAMP (open bars), cholesterol (gray bars), or cholesterol followed by 18 hours of exposure to apo A-I (hatched bars). The defect in apo A-I–mediated cholesterol efflux described for TD cells is reflected by the lack of reduction in ABC1 mRNA after apo A-I treatment in TD1 and TD2 fibroblasts, which is apparent in normal cells (compare hatched bars with gray bars in each group).