title: Calcium chelation induced glutathione efflux from tumor cells and prevention by ruthenium red or neomycin.
abstract: Cultured human lung carcinoma cells (A549) were incubated in a calcium-free medium containing calcium chelators (EGTA, 1-10 mM or BAPTA, 5 mM) for 1 hour at 37 degrees C. With limited toxicity, the presence of calcium chelators resulted in a decrease of cellular GSH and detachment of the cells from the tissue culture flask. The permeable EGTA tetraacetoxymethyl ester (0.5mM-5 mM) caused a decrease in the cellular GSH content without cell detachment. GSH was not oxidized to GSSG nor formed mixed disulfides with protein thiols. AT-125, a gamma-glutamyl transpeptidase inhibitor, prevented detachment, but not the efflux of cellular GSH. Pretreatment with two impermeable compounds (ruthenium red, 100 microM and neomycin, 0.5-10 mM) protected the cells from detachment and prevented the decrease in intracellular GSH. The presence of calcium in the medium during the EGTA and BAPTA treatments also protected the cells. Calcium associated with the cytoplasmic membrane phospholipids or proteins appears important to limit membrane permeability for GSH efflux and to maintain cell attachment.
authors.affiliation: Dept. of Biochemistry and Biophysics, Oregon State University, Corvallis 97331-6503.
authors.forename: A E
authors.initials: AE
authors.lastname: Brodie
authors.forename: D J
authors.initials: DJ
authors.lastname: Reed
mesh_terms: D002118:Calcium / Q000502:physiology*; D002460:Cell Line; D004533:Egtazic Acid / Q000494:pharmacology*; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism*; D019803:Glutathione Disulfide; D006801:Humans; D007555:Isoxazoles / Q000494:pharmacology; D007700:Kinetics; D008175:Lung Neoplasms; D009355:Neomycin / Q000494:pharmacology*; D012430:Ruthenium Red / Q000494:pharmacology*; D005723:gamma-Glutamyltransferase / Q000037:antagonists & inhibitors
chemical_list: D007555:Isoxazoles; D012430:Ruthenium Red; D004533:Egtazic Acid; D005723:gamma-Glutamyltransferase; D005978:Glutathione; D009355:Neomycin; C006303:acivicin; D002118:Calcium; D019803:Glutathione Disulfide