title: Kinetic analysis of rhodamines efflux mediated by the multidrug resistance protein (MRP1).
abstract: Characterization of rhodamine 123 as functional assay for MDR has been primarily focused on P-glycoprotein-mediated MDR. Several studies have suggested that Rh123 is also a substrate for MRP1. However, no quantitative studies of the MRP1-mediated efflux of rhodamines have, up to now, been performed. Measurement of the kinetic characteristics of substrate transport is a powerful approach to enhancing our understanding of their function and mechanism. In the present study, we have used a continuous fluorescence assay with four rhodamine dyes (rhodamine 6G, tetramethylrosamine, tetramethylrhodamine ethyl ester, and tetramethylrhodamine methyl ester) to quantify drug transport by MRP1 in living GLC4/ADR cells. The formation of a substrate concentration gradient was observed. MRP1-mediated transport of rhodamine was glutathione-dependent. The kinetics parameter, k(a) = V(M)/k(m), was very similar for the four rhodamine analogs but approximately 10-fold less than the values of the same parameter determined previously for the MRP1-mediated efflux of anthracycline. The findings presented here are the first to show quantitative information about the kinetics parameters for MRP1-mediated efflux of rhodamine dyes.
authors.affiliation: Laboratoire de Physicochimie Biomoléculaire et Cellulaire, Université Paris Nord, Bobigny, France.
authors.forename: Chantarawan
authors.initials: C
authors.lastname: Saengkhae
authors.forename: Chatchanok
authors.initials: C
authors.lastname: Loetchutinat
authors.forename: Arlette
authors.initials: A
authors.lastname: Garnier-Suillerot
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D045744:Cell Line, Tumor; D002713:Chlorine / Q000737:chemistry; D003630:Daunorubicin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005456:Fluorescent Dyes / Q000494:pharmacology; D005978:Glutathione / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008564:Membrane Potentials; D008956:Models, Chemical; D008962:Models, Theoretical; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000737:chemistry* / Q000502:physiology; D010641:Phenotype; D011188:Potassium / Q000737:chemistry; D020112:Rhodamine 123 / Q000494:pharmacology; D012235:Rhodamines / Q000737:chemistry*; D013997:Time Factors
chemical_list: D002713:Chlorine; D003630:Daunorubicin; D005456:Fluorescent Dyes; D005978:Glutathione; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011188:Potassium; D020112:Rhodamine 123; D012235:Rhodamines; C421109:multidrug resistance-associated protein 1