title: Drug efflux mediated by the human multidrug resistance P-glycoprotein is inhibited by cell swelling.
abstract: P-glycoprotein (P-gp), the product of the human multidrug resistance (MDR1) gene, confers multidrug resistance on cells by acting as an ATP-dependent drug transporter. A method using confocal microscopy was developed to measure the transport activity of P-gp from the rate of movement of doxorubicin, a fluorescent substrate of P-gp, across the membrane of a single cell. Recent work has shown that expression of P-gp enhances the activation of chloride channels in response to cell swelling, suggesting that membrane stretch might switch P-gp from a drug-transporting mode to a mode in which it activates chloride channels. In agreement with this idea, we find that cell swelling inhibits drug efflux in cells expressing P-gp but is without effect on the slower background efflux in cells not expressing P-gp and in cells transiently transfected with a mutated MDR1 in which the ATP hydrolysis sites had been inactivated. The identification of a novel means for inhibiting P-gp-mediated drug transport may have implications for the reversal of multidrug resistance during chemotherapy.
authors.affiliation: Department of Physiology, King's College London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Sardini
authors.forename: G M
authors.initials: GM
authors.lastname: Mintenig
authors.forename: M A
authors.initials: MA
authors.lastname: Valverde
authors.forename: F V
authors.initials: FV
authors.lastname: Sepúlveda
authors.forename: D R
authors.initials: DR
authors.lastname: Gill
authors.forename: S C
authors.initials: SC
authors.lastname: Hyde
authors.forename: C F
authors.initials: CF
authors.lastname: Higgins
authors.forename: P A
authors.initials: PA
authors.lastname: McNaughton
mesh_terms: D016475:3T3 Cells; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002451:Cell Compartmentation; D002463:Cell Membrane Permeability / Q000502:physiology*; D018118:Chloride Channels / Q000378:metabolism; D005576:Colforsin / Q000031:analogs & derivatives / Q000494:pharmacology; D004317:Doxorubicin / Q000378:metabolism*; D018432:Drug Resistance, Multiple / Q000502:physiology*; D006801:Humans; D051379:Mice; D018613:Microscopy, Confocal / Q000379:methods; D009997:Osmotic Pressure; D011994:Recombinant Proteins / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018118:Chloride Channels; D011994:Recombinant Proteins; D005576:Colforsin; D004317:Doxorubicin; D014700:Verapamil; C047983:1,9-dideoxyforskolin