FIGURE 8.
Effects of extracellular pH on Oatp1d1-WT- and Oatp1d1- H102Q-mediated LY uptake kinetics. A, Oatp1d1-WT. Km shifts from 27.0 ± 4.4 μm in neutral pHo to 134 ± 13.1 μm in pHo 8, whereas at the same time it remains unchanged at acidic pHo. Vm is significantly reduced at pHo 8 (83.1 nmol/mg protein/min; c.i. 76.5–90.0) in relation to neutral pHo (91.2 nmol/mg protein/min; c.i. 81.4–101), while at the same time Vm significantly increases at acidic pHo (110 nmol/mg protein/min; c.i. 103–117). B, Oatp1d1-H102Q. Similar to Oatp1d1-WT, Km remains the same at acidic pHo (22.9 ± 2.5 μm relative to neutral pHo (21.9 ± 5.2 μm), whereas Vm is significantly increased at acidic pHo (157 nmol/mg protein/min; c.i. 146–168) relative to neutral pHo (119 nmol/mg protein/min; c.i. 97.7–134). The uptake into vector-transfected HEK293 cells (mock cells) was subtracted to obtain transporter-specific uptake, and data were fitted in GraphPad Prism version 5. Each value represents the mean ± S.E. (error bars) from triplicate determinations.