Fig. 6.
MβCD inhibits ASBT activity in human intestinal Caco-2 cells. A: postconfluent Caco-2 cells were incubated with either 10 mM MβCD alone or with 10 mM MβCD + 1.25 mM cholesterol for 1 h at 37°C. Na+-dependent [3H]TC uptake (10 μM) was then determined for 5 min. Results are presented as % of control and are means ± SE obtained from 5 separate experiments. *P < 0.05 compared with control. B: postconfluent Caco-2 cells were incubated with vehicle alone (●) or with 10 mM MβCD (◯) for 1 h at 37°C, and Na+-dependent TC uptake was performed in the presence of increasing concentrations of the substrate TC. Sodium-dependent TC uptake was expressed as pmol•mg protein−1 •5 min−1. Experiments were performed 4 times in triplicate in separate groups of cells. Michaelis-Menten plot of a representative experiment is shown. Results indicate a decrease in the Vmax of the transport process from 63 ± 8 (control) to 35 ± 4 pmol•mg protein−1 •5 min−1 in MβCD-treated cells.