FIGURE 7.

pH dependence of Oatp1d1. A, extracellular acidification (pH_o) activates Oatp1d1-mediated LY uptake by 2.5-fold. When the inwardly directed [H]⁺ gradient is stopped with 2 μm monensin, LY uptake returns to control levels at neutral pH_o. B, intracellular acidification after incubation in 30 mm NH₄Cl (30 min at 37 °C), which creates an outwardly directed [H]⁺ gradient, abolishes Oatp1d1 LY uptake after pH_i is reduced by 1.25 pH units (acidification from pH 7.35 to 6.05). Each data point represents the mean ± S.E. (error bars) of three independent experiments.