Long term myriocin treatment increases MRP1 transport activity

Long term myriocin treatment increases the activity of MRP1 as well as its association with lipid rafts. (A) Efflux assays were performed in long term (7 day) myriocin-treated and control cells using 5-carboxyfluorescein as a substrate for MRP1 in BHK-MRP1 cells. The Y-axis represents the remaining fluorescent substrate relative to the starting value at t=0min (=100%). Data represent the mean±SD (n=3). At 10min the inhibitor controls are also presented, using MK571. ♦ solid line: control, untreated cells; ■ dotted line: myriocin-treated cells. (B) Lipid raft association of MRP1 was determined in long term (7 day) myriocin-treated and control cells. Values indicate the percentage of MRP1 found in the gradient fractions, relative to total amount in the entire gradient (9 fractions). White bars, control cells; black bars, myriocin-treated cells. Data represent the mean±SD of three independent experiments. Asterisks indicate values that are significantly different from the control condition (P