Fig. 2.

SLC46A3 mediates proton-coupled estrone 3-sulfate uptake. (A) Uptake of [³H]estrone 3-sulfate (10 nM), methotrexate (10 μM), [³H]nicotinate (200 nM), [³H]palmitate (20 nM), and [¹⁴C]urate (1.8 μM) with 50 μM urate in MDCKII/SLC46A3 dC cells. Uptake for 5 min was measured in HBSS (pH 5.5). Relative uptake was calculated by dividing the uptake in MDCKII/SLC46A3 dC cells by that in mock cells. (B) pH dependence of [³H]estrone 3-sulfate (10 nM) uptake. Uptake for 1 min was measured in HBSS (pH 7.4) or modified-HBSS-containing citrate for pH 4.0 to 4.5, or MES for pH 5.0 to 6.5. (C) Effect of a proton gradient on [³H]estrone 3-sulfate uptake. The uptake was measured in HBSS (pH 5.0) or modified-HBSS in which NaCl was replaced with KCl with or without 10 μg/mL nigericin. (D) Concentration-dependent estrone 3-sulfate uptake. Uptake for 1 min was measured in HBSS (pH 5.0). SLC46A3 dC-specific uptake was calculated by subtracting the uptake in mock cells from that in MDCKII/SLC46A3 dC cells. The solid line represents the computer-fitted profile. Data are represented as the mean ± SEM obtained from two biologically independent experiments. P-values are indicated in the different panels (one-way ANOVA followed by Tukey's multiple comparisons test).