title: Cooperative P-glycoprotein mediated daunorubicin transport into DNA-loaded plasma membrane vesicles.
abstract: Most of the multidrug resistant human tumor cell lines overexpress the MDR1 gene product P-glycoprotein (P-gp) which is believed to function as an energy-dependent drug efflux pump. Here we describe a novel method that allows the kinetic characterization of P-gp-mediated active drug transport. This method is based on the fluorescence quenching of anthracyclines transported into DNA-loaded plasma membrane vesicles. The uptake of daunorubicin (DNR) into the plasma membrane vesicles was saturable in terms of the extravesicular DNR concentration with a Km of 1.5 +/- 0.1 microM. This transport occurred by a cooperative process with a Hill coefficient close to 2 for DNR. A model is discussed in which P-gp pumps two molecules of drug per turnover.
authors.affiliation: Free University Hospital, Department of Medical Oncology, Amsterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Guiral
authors.forename: O
authors.initials: O
authors.lastname: Viratelle
authors.forename: H V
authors.initials: HV
authors.lastname: Westerhoff
authors.forename: J
authors.initials: J
authors.lastname: Lankelma
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000255:Adenosine Triphosphate / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D003630:Daunorubicin / Q000378:metabolism*; D004351:Drug Resistance; D005260:Female; D006801:Humans; D007700:Kinetics; D008081:Liposomes / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000378:metabolism*; D010051:Ovarian Neoplasms; D013050:Spectrometry, Fluorescence; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002352:Carrier Proteins; D008081:Liposomes; D008562:Membrane Glycoproteins; D000255:Adenosine Triphosphate; D004247:DNA; D014700:Verapamil; D008274:Magnesium; D003630:Daunorubicin