Figure 1. Concentration-dependent cytotoxicity (a) and cellular accumulation (b) of OXA in mock and hOCTN1-, hOCT2-, hOCTN2-transfected MDCK cells. For the cytotoxicity study, the cells were incubated in the absence or presence of OXA for 48 h; for the cellular accumulation study, the cells were incubated with OXA (40 μM) for 5 min. Data are expressed as the mean ± SEM, n = 6 for cell toxicity and n = 5 for OXA accumulation. Compared with the mock cells,##P < 0.01,###P < 0.001.