Cellular accumulation rates of platinum after 2-hour exposure to cisplatin, carboplatin, and oxaliplatin. The cellular accumulation rates of platinum in OCT1-transfected (A), OCT2-transfected (B), and OCT3-transfected (C) cells and in the corresponding MOCK cells after incubation with cisplatin, carboplatin, and oxaliplatin in the presence (white columns) or absence (black columns) of an OCT inhibitor (disopyramide for OCT1 and cimetidine for OCT2 and OCT3) were determined as described in Materials and Methods. Briefly, MDCK cells (A) were incubated in the antibiotic-free medium containing cisplatin (6 μmol/L), carboplatin (20 μmol/L), or oxaliplatin (6 μmol/L) at 37°C and 5% CO2 for 2 hours. For the inhibitor studies, the incubation medium also contained disopyramide (150 μmol/L). B, HEK 293 cells were incubated in the antibiotic-free medium containing cisplatin (0.3 μmol/L), carboplatin (10 μmol/L), or oxaliplatin (0.3 μmol/L) at 37°C and 5% CO2 for 2 hours. For the inhibitor studies, the incubation medium also contained cimetidine (1.5 mmol/L). C, the study was done similarly as in (B), except that the concentrations of cisplatin, carboplatin, and oxaliplatin in the incubation medium were 2, 10, and 2 μmol/L, respectively. Columns, mean of six measurements for OCT1 and OCT2 and of three measurements for OCT3; bars, SD.