title: Significant differences between procyclic and bloodstream forms of Trypanosoma brucei in the maintenance of their plasma membrane potential.
abstract: The plasma membrane potential (deltapsi) of procyclic and bloodstream trypomastigotes of Trypanosoma brucei was studied using the potentiometric fluorescent dye bisoxonol. Our results suggest that a proton pump plays a significant role in the regulation of deltapsi in procyclic and bloodstream forms, as evidenced by depolarization of the plasma membrane by H(+)-ATPase inhibitors (e.g. dicyclohexylcarbo-diimide, N-ethylmaleimide, diethylstilbestrol, and bafilomycin A1). In bloodstream stages the plasma membrane was significantly depolarized by ouabain only when the cells were incubated in sodium-rich buffers indicating that a sodium pump was being inhibited. In contrast, ouabain had no effect on the deltapsi of the procyclic stages in a sodium-rich buffer. However, it induced an additional significant depolarization in these stages when their plasma membrane was already partially depolarized by the H(+)-ATPase inhibitor dicyclohexylcarbo-diimide, indicating the presence of an ouabain-sensitive sodium pump whose activity is masked by the H(+)-ATPase. Unlike procyclic forms, the deltapsi of bloodstream-stage trypomastigotes was markedly sensitive to extracellular Na+ and K+ concentrations. Thus, there are significant differences between procyclic and bloodstream forms in the maintenance of the deltapsi and in their permeability to cations.
authors.affiliation: Department of Pathobiology, University of Illinois at Urbana-Champaign, 61802, USA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Van der Heyden
authors.forename: Roberto
authors.initials: R
authors.lastname: Docampo
mesh_terms: D000818:Animals; D001769:Blood / Q000469:parasitology; D002462:Cell Membrane / Q000502:physiology*; D002463:Cell Membrane Permeability; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase; D013696:Temperature; D014346:Trypanosoma brucei brucei / Q000254:growth & development* / Q000502:physiology
chemical_list: D006180:Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase