Abstract
MRP1 activity was evaluated and compared in 11 cell lines with different levels of MRP1 expression using functional assays of calcein acetoxymethyl ester (calcein-AM), carboxyfluorescein diacetate (CFDA) and Rhodamine 123 (Rh123) in combination with the modulators cyclosporin A (CsA), probenecid and MK571. A good correlation was found between MRP1 expression and the modulatory effect of MK571 on calcein-AM uptake ( P=0.01) and probenecid effect on CFDA uptake ( P=0.02). Additionally, the combined modulatory effect of MK571 and probenecid on CFDA uptake ( P<0.0001) and on calcein-AM uptake ( P=0.0001) were highly significant. No correlation was found between MRP1 expression and the effects of three modulators on Rh123 uptake or efflux. In conclusion, calcein-AM and CFDA uptake assays are the best choices to probe MRP1 activity and combination of two modulators may improve the efficiency of these assays.
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