title: Efficiency of P-glycoprotein-mediated exclusion of rhodamine dyes from multidrug-resistant cells is determined by their passive transmembrane movement rate.
abstract: The aim of the present study was to examine the relationship between the rate of the passive transmembrane movement of multidrug resistance (MDR)-type substrates and the ability of P-glycoprotein to extrude them from MDR cells. For this purpose, seven rhodamine dyes were examined for their P-glycoprotein-mediated exclusion from MDR cells, their localization in wild-type drug-sensitive cells, their capacity to stimulate the ATPase activity of P-glycoprotein reconstituted in proteoliposomes, and their transmembrane movement rate in artificial liposomes. All these rhodamine dyes were accumulated in wild-type drug-sensitive cells and were localized mainly in the mitochondria. All the dyes tested were substrates of reconstituted P-glycoprotein and cellular P-glycoprotein and were excluded to a variable degree from MDR cells. The transmembrane movement rate proved the major factor determining the efficacy of the P-glycoprotein-mediated exclusion of rhodamine dyes from MDR cells. Thus, rhodamine B, the poorest cellular P-glycoprotein substrate, exhibited a high affinity toward reconstituted P-glycoprotein, but was the fastest membrane-traversing dye. In contrast, tetramethylrosamine, the best cellular MDR probe, exhibited high affinity toward reconstituted P-glycoprotein and slow transmembrane movement rate. Therefore, an anticancer drug with a fast transmembrane movement rate is expected to overcome the MDR phenomenon. Furthermore, the widely used MDR marker, rhodamine 123, was a poor cellular MDR substrate compared with other rhodamine dyes, especially tetramethylrosamine, which was a superior cellular MDR substrate for functional dye-exclusion studies.
authors.affiliation: Department of Biology Technion-Israel Institute of Technology, Haifa. eytan@tx.technion.ac.il
authors.forename: G D
authors.initials: GD
authors.lastname: Eytan
authors.forename: R
authors.initials: R
authors.lastname: Regev
authors.forename: G
authors.initials: G
authors.lastname: Oren
authors.forename: C D
authors.initials: CD
authors.lastname: Hurwitz
authors.forename: Y G
authors.initials: YG
authors.lastname: Assaraf
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D018432:Drug Resistance, Multiple / Q000502:physiology*; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000737:chemistry / Q000493:pharmacokinetics*; D006801:Humans; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism; D015335:Molecular Probes; D011510:Proteolipids; D020112:Rhodamine 123; D012235:Rhodamines / Q000737:chemistry / Q000493:pharmacokinetics*; D013050:Spectrometry, Fluorescence; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D005456:Fluorescent Dyes; D015335:Molecular Probes; D011510:Proteolipids; D012235:Rhodamines; C020485:proteoliposomes; D020112:Rhodamine 123; D000251:Adenosine Triphosphatases