Correlation Engine 2.0
Clear Search sequence regions

A convenient functional assay of the multidrug resistance (MDR) pump is useful for the diagnosis of MDR-1 cancers and the quantitative determination of the potency of inhibitors of the pump. Calcein-AM, a substrate of the MDR pump, was used to determine the concentration of SDZ PSC833 needed to completely inhibit the pump in CEM/VLB100 drug-resistant cells. The initial rates (in percent) for calcein retention by these MDR-1 cells were used to calculate values for the percent initial efflux of calcein-AM through the MDR pump in the presence of the inhibitors PSC833, cyclosporinA, and dexniguldipine. The percent efflux values at 250 and 60 nM calcein-AM were used to calculate the required concentration of each inhibitor to produce half-inhibition (I50) of initial efflux through the pump. These results are consistent with a noncompetitive inhibition of the MDR pump by each of the three inhibitors. Copyright 1999 Academic Press.


P W Wigler. PSC833, cyclosporin A, and dexniguldipine effects on cellular calcein retention and inhibition of the multidrug resistance pump in human leukemic lymphoblasts. Biochemical and biophysical research communications. 1999 Apr 13;257(2):410-3

Expand section icon Mesh Tags

Expand section icon Substances

PMID: 10198227

View Full Text