title: Calcium mobilization by arachidonic acid in trypanosomatids.
abstract: A recent report (Eintracht J, Maathai R, Mellors A, Ruben L. Calcium entry in Trypanosoma brucei is regulated by phospholipase A, and arachidonic acid, Biochem J 1998:336:659-66) provided evidence that calcium entry in Trypanosoma brucei bloodstream trypomastigotes is regulated via a signaling pathway involving phospholipase A2-mediated generation of arachidonic acid and stimulation of a plasma membrane-located calcium channel. Here we show that Ca2+ influx in T. brucei procyclic trypomastigotes, Leishmania donovani promastigotes and T. cruzi amastigotes was also stimulated in a dose-dependent manner (50-400 nM) by the amphiphilic peptide melittin. This effect was blocked by the phospholipase A, inhibitor 3-(4-octadecyl)-benzoylacrylic acid. The unsaturated fatty acid arachidonic acid, in the range of 10-75 microM, induced Ca2+ entry by a mechanism sensitive to LaCl3. However, both melittin and arachidonic acid induced an increase in [Ca2+]i in T. brucei procyclic trypomastigotes incubated in Ca2+-free medium implying Ca2+ mobilization from intracellular stores. This hypothesis was supported by experiments showing that arachidonic acid promoted Ca2+ release from the acidocalcisomes of these cells. The results showing changes in mitochondrial membrane potential, release of acridine orange and Ca2+ from the acidocalcisomes and Ca2+ transport across the plasma membrane suggest that in addition to the possible stimulation of a Ca2+ channel-mediated process, arachidonic acid, in the range of concentrations used here, have other nonspecific effects on the trypanosomatids membranes.
authors.affiliation: Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana 61802, USA.
authors.forename: R
authors.initials: R
authors.lastname: Catisti
authors.forename: S A
authors.initials: SA
authors.lastname: Uyemura
authors.forename: R
authors.initials: R
authors.lastname: Docampo
authors.forename: A E
authors.initials: AE
authors.lastname: Vercesi
mesh_terms: D000165:Acridine Orange / Q000378:metabolism; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism* / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D003470:Culture Media; D007052:Ibuprofen / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology; D008555:Melitten / Q000494:pharmacology; D008564:Membrane Potentials; D008928:Mitochondria / Q000502:physiology; D015388:Organelles / Q000378:metabolism; D014351:Trypanosomatina / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
chemical_list: D003470:Culture Media; C028521:lanthanum chloride; D008555:Melitten; D016718:Arachidonic Acid; D007811:Lanthanum; D000165:Acridine Orange; D002118:Calcium; D007052:Ibuprofen