title: Active transport of glutathione S-conjugate in human colon adenocarcinoma cells.
abstract: The formation of the glutathione S-conjugate of monochlorobimane (GSH-bimane) in human colon adenocarcinoma cells was identified by HPLC-fluorimetry and its transport from the cells was found to be temperature-sensitive, saturable and ATP-dependent. The apparent K(m) and Vmax values were 2.4 +/- 0.5 nmol GSH-bimane/10(6) cells and 0.5 +/- 0.1 nmol GSH-bimane/min per 10(6) cells, respectively. This active transport of GSH-bimane was inhibited by low micromolar concentrations of classical uncouplers of oxidative phosphorylation, namely carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), carbonylcyanide m-chlorophenylhydrazone (CCCP) and 2,4-dinitrophenol (DNP). The efflux of GSH-bimane was competitively inhibited by chlorambucil (CMB) and 1-chloro-2,4-dinitrobenzene (CDNB), two other substrates of GST. This study demonstrates the presence and kinetic measurements of the glutathione S-conjugate export (GS-X) pump in human colon cancer cells, an export pump whose function has been implicated in the phenomenon of multidrug resistance.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, National University of Singapore, Kent Ridge, Singapore.
authors.forename: K
authors.initials: K
authors.lastname: Zhang
authors.forename: K P
authors.initials: KP
authors.lastname: Wong
mesh_terms: D019297:2,4-Dinitrophenol / Q000494:pharmacology; D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology; D001693:Biological Transport, Active; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D002699:Chlorambucil / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology*; D004137:Dinitrochlorobenzene / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005470:Fluorometry; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D026901:Membrane Transport Proteins; D010085:Oxidative Phosphorylation / Q000187:drug effects; D011720:Pyrazoles / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D002352:Carrier Proteins; D004137:Dinitrochlorobenzene; D026901:Membrane Transport Proteins; D011720:Pyrazoles; D014475:Uncoupling Agents; C086860:glutathione transporter; D002699:Chlorambucil; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; C059597:monochlorobimane; D000255:Adenosine Triphosphate; D005978:Glutathione; D019297:2,4-Dinitrophenol