Fig. 3.
Inhibition of MRP4-mediated transport of [3H]DHEAS by TS in membrane vesicles from MRP4-overexpressing and control human embryonic kidney 293T cells. (A) Effect of GSH (3 mM) on MRP4-mediated transport of 2 μM [3H]DHEAS and inhibition by 10 μM TS. (B) Effect of increasing concentrations of TS (0, 5, 10, and 50 μM) on MRP4-mediated [3H]DHEAS (2 minutes, 0.5–20 μM) transport in the absence of GSH. Each point represents the mean ± S.D. A noncompetitive inhibition model best described the data. Lines represent model fits based on the noncompetitive inhibition model. Representative plots from n = 2 independent studies are presented. The estimated Ki values based on a noncompetitive inhibition model were 8.0 ± 0.7 and 8.5 ± 1.2 µM from each study.