Fig. 1.

Time course of OCT2-mediated uptake of 0.31 µM [³H]MPP (A), 13.9 µM [¹⁴C]metformin (B), 0.0218 µM [³H]TEA (C), 0.0134 µM [³H]cimetidine (D), 3 µM NBD-MTMA (E), and 10 µM ASP (F). Uptakes are reported as clearance (microliters per square centimeter). These data represent OCT2-mediated transport (i.e., uptake in wild-type CHO cells was subtracted from total substrate uptake measured in OCT2-expressing cells). Each data point is the mean ± S.E. determined in two experiments (MPP, metformin, cimetidine, TEA, and ASP) or three experiments (NBD-MTMA), each using three to five replicate wells. The lines fit to the data for MPP, metformin, TEA, and cimetidine were calculated using an exponential one-phase association function (Prism; GraphPad); the uptakes of NBD-MTMA and ASP were described by simple linear regression.