Accumulation of 1 μM Fl-MTX or 1 μM Na-Fluo at 37°C for 10 minutes at pH 7.4 was measured in the absence (nt) or presence of various compounds. Activity is determined by comparing the percentage of fluorescence compared to control, non-treated cells. Bars represent the average values of at least three independent experiments (+/− SD). nt: non-treated control, CsA: 20 μM cyclosporin A, UA: 20 μM ursolic acid, CA: 150 μM cholic acid, GC: 150 μM glycocholate, TC: 150 μM taurocholate, EG: 50 μM estradiol 17-β–D-glucuronide, PGE2: 5 μM prostaglandin E2, Rif: 10 μM rifampicin, and MTX: 10 μM methotrexate. Significantly different form the non-treated control: * p< 0.05, ** p<0.01, *** p<0.001.