title: Anion effects on vesicle acidification in Dictyostelium.
abstract: Chloride ions stimulated the ATP-dependent formation of a proton gradient in vesicles derived from amoebae of the cellular slime mould, D. discoideum, and reduced the formation of a membrane potential, inhibited rather than stimulated the formation of the proton gradient. Since bicarbonate ions did not inhibit H(+)-ATPase activity we conclude that they enter the vesicles and combine with translocated protons. This finding is consistent with the suggestion that the membranes of the light vesicle fraction are fragments of contractile vacuole complexes, and that these organelles increase their osmotic activity by taking up bicarbonate ions and protons from the cytoplasm, and then release water and carbonic acid into the extracellular milieu.
authors.affiliation: Department of Biochemistry, University of Oxford, United Kingdom.
authors.forename: C
authors.initials: C
authors.lastname: Giglione
authors.forename: J D
authors.initials: JD
authors.lastname: Gross
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000494:pharmacology; D000165:Acridine Orange; D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology*; D004023:Dictyostelium / Q000201:enzymology* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D007555:Isoxazoles; D008564:Membrane Potentials; D015388:Organelles / Q000737:chemistry / Q000187:drug effects; D017494:Proton Pumps / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism*
chemical_list: D001639:Bicarbonates; D002712:Chlorides; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007555:Isoxazoles; D017494:Proton Pumps; C013633:oxonol V; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D009327:4-Chloro-7-nitrobenzofurazan; D000165:Acridine Orange