title: Vinblastine transport by membrane vesicles from human multidrug-resistant CCRF-CEM leukaemia cells: inhibition by taxol and membrane permeabilising agents.
abstract: Inside-out membrane vesicles prepared from multidrug resistant human leukemic cells (CEM/VBL1000), but not from sensitive cells, transported [3H]-labelled vinblastine (VBL) in an ATP-dependent manner, reaching a plateau level by 15 min. The transport occurred with an apparent Km of 60 +/- 20nM. Verapamil (10 microM), and taxol (IC50 = 1 microM) prevented VBL uptake and evoked VBL diffusion from vesicles when added after VBL uptake had reached steady state. The channel forming agent alamethicin prevented net uptake of VBL and addition of alamethicin to the vesicles after the steady-state had been reached resulted in the rapid efflux of [3H]VBL. Very low concentrations of Triton X-100 (0.01 % v/v) also prevented net uptake of VBL, whilst addition of Triton X-100 and making the medium hypo-osmotic after the steady state had been reached caused the [3H]VBL to rapidly diffuse out of the vesicles. These observations indicate that VBL is actively transported into the lumen of inside-out vesicles from multidrug resistant leukaemia cells.
authors.affiliation: Department of Pharmacy, University of Sydney, NSW, Australia.
authors.forename: S K
authors.initials: SK
authors.lastname: Syed
authors.forename: R I
authors.initials: RI
authors.lastname: Christopherson
authors.forename: B D
authors.initials: BD
authors.lastname: Roufogalis
mesh_terms: D000408:Alamethicin / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D004351:Drug Resistance; D006801:Humans; D007945:Leukemia, Lymphoid / Q000378:metabolism*; D017830:Octoxynol / Q000494:pharmacology; D009994:Osmolar Concentration; D017239:Paclitaxel / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology; D014747:Vinblastine / Q000493:pharmacokinetics*
chemical_list: D000408:Alamethicin; D014747:Vinblastine; D017830:Octoxynol; D014700:Verapamil; D000254:Sodium-Potassium-Exchanging ATPase; D017239:Paclitaxel