title: Reversal agent inhibition of the multidrug resistance pump in human leukemic lymphoblasts.
abstract: Multidrug resistant cancer cells of the MDR-1 phenotype utilize an ATP-dependent pump to excrete toxic drugs. Rhodamine 123 (R123) is a fluorescent substrate of the MDR pump. An assay for the ATP-dependent initial efflux of R123 from CEM/VLB100 human leukemic lymphoblasts has been developed. The MDR-1 cells were treated with a reversal agent and preloaded with 40.0 nM R123 in buffer at 30 degrees C that contained sodium azide and 2-deoxyglucose. The cells were rinsed with cold buffer and resuspended in L-glutamine/glucose solution at 23 degrees C. The cell suspension was passed through a filter and R123 in the filtrate was detected at 2-s intervals by fluorescence. Efflux of R123 was inhibited by the reversal agents amiodarone, cyclosporin A, Ro11-2933 (DMDP), quinidine, and the optical isomers of propranolol. The MDR pump is stereospecific for the (R)-diastereomer quinidine; however, the (S)-diastereomer quinine is a relatively weak inhibitor of the pump. Cyclosporin A was the most potent inhibitor tested against the efflux of R123 by the MDR pump.
authors.affiliation: Department of Medical Biology, University of Tennessee Medical Center, Knoxville 37920.
authors.forename: P W
authors.initials: PW
authors.lastname: Wigler
authors.forename: F K
authors.initials: FK
authors.lastname: Patterson
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000638:Amiodarone / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors*; D016572:Cyclosporine / Q000494:pharmacology; D004351:Drug Resistance; D006801:Humans; D007938:Leukemia / Q000378:metabolism* / Q000473:pathology; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors*; D011433:Propranolol / Q000494:pharmacology; D011437:Propylamines / Q000494:pharmacology; D011802:Quinidine / Q000494:pharmacology; D011803:Quinine / Q000494:pharmacology; D020112:Rhodamine 123; D012235:Rhodamines; D013237:Stereoisomerism; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D011437:Propylamines; D012235:Rhodamines; D020112:Rhodamine 123; D016572:Cyclosporine; C054970:Ro 11-2933; D011433:Propranolol; D011803:Quinine; D011802:Quinidine; D000638:Amiodarone