Figure 2. Effect of preincubation time with BI01383298 on NaCT-mediated citrate uptake in HepG2 cells.

(A) HepG2 cells were preincubated in NaCl buffer, pH 7.5, either without (●) or with 10 mM LiCl buffer (○) in the absence or presence of 10 µM BI01383298 for the indicated time periods. Cells were then washed twice to remove the inhibitor and then used for uptake measurement. Uptake of [¹⁴C]-citrate was measured for 30 min with the respective preincubation buffer, but in the absence of BI01383298 (the inhibitor was present only during preincubation but absent during uptake). (B) HepG2 cells were preincubated in NaCl buffer, pH 7.5, either without (●) or with 10 mM LiCl buffer (○) with increasing concentrations of BI01383298 for 30 min. Cells were then washed twice to remove the inhibitor and then used for uptake measurement. Uptake of [¹⁴C]-citrate was measured for 30 min with the preincubation buffer but in the absence of BI01383298 (the inhibitor was present at different concentrations only during preincubation but absent during uptake). The uptake values were higher when measured in the presence of Li⁺ than in the absence of Li⁺ as expected of human NaCT. The concentration of citrate was 7.0 µM for the uptake assay in the absence of Li⁺, and 3.5 µM for the uptake assay in the presence of Li⁺. Data (means ± S.D.) are presented as percent of the respective control uptake in each case.