Figure 2.

Inhibition of [³H]preS1 peptide binding and [³H]TC transport by betulin derivatives. NTCP-HEK293 cells were incubated with tetracycline in order to induce NTCP expression and were used for bile acid transport experiments with 1 µM [³H]TC and for myr-preS1_2-48 lipopeptide binding experiments with 5 nM [³H]preS1, each over 10 min at 37 °C. Cells without tetracycline treatment were used as 0% controls of [³H]TC uptake and [³H]preS1 binding, respectively. Experiments were performed with solvent alone (set to 100%) and with increasing concentrations of the indicated inhibitor. The mean of the 0% control was subtracted to calculate net [³H]TC transport rates (shown in blue) as well as net [³H]preS1 binding rates (shown in red), both expressed as % of control at the y-axis. Half maximal inhibitory concentrations (IC₅₀) were calculated by nonlinear regression analysis using the equation log(inhibitor) vs. response (GraphPad Prism). The figure shows selected diagrams. Chemical structures of the compounds are depicted in Table 1, the respective IC₅₀ values are listed in Table 2. Data represent means ± SD of quadruplicate determinations (n = 4).