(A) The uptake of MPP+, dopamine, serotonin, epinephrine, norepinephrine, uridine, adenosine by MDCK/hPMAT (closed bars), MDCK/rPmat (grey bars) or MDCK/mock (open bars) cells was measured for 3 min at 37 °C and pH 7.4. (B) The uptake of MPP+, dopamine, serotonin, epinephrine, norepinephrine, uridine, adenosine by Flp293/mPMAT (hatched bars) or Flp293/mock (open bars) cells was measured for 2 min at 37 °C and pH 7.4. The total applied concentration of a test compound was 1 µM containing 0.1 µCi of the [H3]-labeled form. The uptake of uridine and adenosine were determined in the presence of 0.5 µM NBMPR, which is a potent inhibitor of endogenous nucleoside uptake by MDCK and Flp293 cells. *P < 0.05, significantly different from MDCK/mock or Flp293/mock cells. Data are shown as the mean ± SEM (n = 6).