Fig. 1.

Effect of micellar cholesterol on ABCA1-mediated efflux of endogenous cholesterol. Caco-2 cells were labeled for 18 h with 2.5 μCi of [³H]cholesterol. After labeling, cells were washed and placed in new wells with the basal medium containing 3 μg/ml apolipoprotein A-I (apoA-I). Increasing amounts of cholesterol solubilized in 5 mM taurocholate micelles were added to the apical medium with 0 (open bars) or 2 μM (hatched bars) of the liver X receptor agonist T0901317. At the end of an 18 h incubation, the following were estimated: (A) cellular [³H]cholesteryl esters; (B) percent of [³H]cholesterol effluxed into the basal medium; (C) cholesterol mass effluxed into the basal medium; (D) ABCA1 mRNA; (E) ABCA1 mass. The data represent the mean ± SE of 6 dishes. * P < 0.05 versus cells incubated without cholesterol or T0901317. ^§ P < 0.05 versus cells incubated without cholesterol but with T0901317.