Fig. 5.

[³H]taurocholic acid (TCA) uptake assay in transfected Huh7 cells. A: uptake of 10 µM [³H]TCA in cells transiently transfected with empty vector (control), hNTCP, or skSlc10a1. Cells were incubated for 10 min in medium containing Na⁺ (+) or medium where Na⁺ was substituted with choline (–). *P < 0.05 vs. choline. Kinetics of [³H]TCA uptake in cells transfected with hNTCP (B) or skSlc10a1 (C). Cells were incubated for 10 min, and background uptake levels derived from cells transfected with vector control were subtracted. Data were normalized to total cell protein. Kinetic parameters were obtained by nonlinear curve fitting using the Michaelis-Menten equation. Competition assays for uptake of [³H]TCA and scymnol sulfate in hNTCP (D) and skSlc10a1 (E) in transfected Huh7 cells. Cells were incubated with indicated concentrations of TCA and scymnol sulfate for 10 min. The calculated K_i of scymnol sulfate for hNTCP and skSlc10a1 are 3.5 ± 0.57 µM (mean ± SD) and 31 ± 5 µM, respectively from three independent experiments. A representative plot is presented.