Further Evidence for the Existence of a Membrane Potential in Trypanosoma brucei brucei

Midgley, M.

doi:10.1099/00221287-129-8-2677

Cited by 3 publications

(2 citation statements)

References 9 publications

(14 reference statements)

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“…It would be expected that the distribution of Cst and Rb' would report the K t diffusion potential in the presence of valinomycin equally well. However, it is significant that, in this present study, the extracellular medium contained K ' (6.2 mM), whereas the experiments described by Midgley (1983b) were performed in a K'-free medium, and hence the AY, in the absence of extracellular K + was likely to be hyperpolarized. It should be noted that the distribution of Rb' or Cs' cannot be used to assess an intracellular A Y , since intracellular organelles such as mitochondria usually possesses no passive electrical permeability to K + or its analogues (Scott and Nicholls, 1980).…”

Section: Discussionmentioning

confidence: 83%

The distribution of permeant ions demonstrates the presence of at least two distinct electrical gradients in bloodstream forms of Trypanosoma brucei

Nolan

Voorheis

1991

European Journal of Biochemistry

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The distribution of 86Rb+ and the radiolabelled lipophilic cation [3H]methyltriphenylphosphonium (MePh3P+) was used to investigate the membrane potentials that exist in bloodstream forms of Trypanosoma brucei. Even after correction for binding to cellular constituents, the accumulation of MePh3P+ was approximately tenfold greater than the accumulation of Rb+ under resting conditions. The addition of low concentrations of carbonylcyanide p‐trifluoromethoxyphenylhydrazone or valinomycin reduced the accumulation of MePh3P+ tenfold without perturbing the accumulation of Rb+. Although selective permeabilization of the plasma membrane abolished the accumulation of Rb+ and caused a substantial decrease in the accumulation of MePh3P+, a significant carbonylcyanide‐p‐trifluoromethoxyphenylhydrazone‐sensitive accumulation of MePh3P+ persisted under these conditions. These data were consistent with the presence of at least two distinct membrane potentials (Ψ) in bloodstream forms of T. brucei; a potential across the plasma membrane (Ψp) and an additional Ψ, generated by the electrogenic movement of H+, across the membrane of an intracellular organelle that possesses no electrical permeability to Rb+ or K+.

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Section: Discussionmentioning

confidence: 83%

The distribution of permeant ions demonstrates the presence of at least two distinct electrical gradients in bloodstream forms of Trypanosoma brucei

Nolan

Voorheis

1991

European Journal of Biochemistry

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“…However, it is only recently that several studies have contributed to a better understanding of the bioenergetics of this protozoon. Early studies [1,2] established the existence of a membrane potential. Recently, the transmembrane potentials (∆Ψ) and the pH gradient (∆pH), components of the proton electrochemical potential (∆µ H + ), were intensively investigated in various laboratories for the bloodstream form of T. brucei brucei using distribution of radioactive cations (Rb + , methyltriphenylphosphonium, tetraphenylphosphonium), weak acids and weak bases.…”

Section: Introductionmentioning

confidence: 99%

Kinetic study of the plasma-membrane potential in procyclic and bloodstream forms of Trypanosoma brucei brucei using the fluorescent probe bisoxonol

Defrise-Quertain

Fraser-L’Hostis

Coral

et al. 1996

Biochemical Journal

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The characteristics of the plasma-membrane potential of procyclic and bloodstream forms of Trypanosoma brucei brucei (cultured cells) were investigated using the fluorescent anionic probe bisoxonol. Observation of a stable and representative plasma-membrane potential in the resting state required careful washing, centrifugation and maintenance of the cells at room temperature before measurement. Bloodstream forms were more prone to depolarization during washing at 4 degrees C than procyclic cells. The higher fluorescence observed in the presence of long slender cells than in the presence of procyclic cells shows that the plasma-membrane potential is more negative in the insect form. Healthy dilute cells can sustain their plasma-membrane potential for hours in the presence of external glucose. The presence of a high K+ concentration in the medium did not promote by itself the depolarization of either type of cell. Study of bisoxonol fluorescence as a function of time allowed us to follow the kinetics of the action of metabolic inhibitors in the presence of various ions. o-Vanadate (1 mM) was found to depolarize bloodstream-form cells rapidly but only in a phosphate-free NaCl buffer. Omeprazole and strophanthidin also specifically depolarized bloodstream-form trypanosomes. However, NN'-dicyclohexylcarbodi-imide depolarized both types of cell, but more rapidly for bloodstream-form cells. Bloodstream-form trypanosomes appear to use mainly a vanadate-sensitive Na+ pump to maintain their Na+-diffusion gradient. However, most of the ATPase inhibitors tested had little or no effect on the plasma-membrane potential of procyclics suggesting that this form of trypanosome may rely on several regulation mechanisms.

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Membrane-related processes and overall energy metabolism inTrypanosoma brucei and other kinetoplastid species

Kuile

1994

J Bioenerg Biomembr

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An electrochemical proton gradient exists across the plasma membrane and the mitochondrial membrane of the bloodstream form of Trypanosoma brucei. The membrane potential across the plasma membrane and the regulation of the internal pH depend on the temperature. Leishmania donovani regulates its internal pH and maintains a constant electrochemical proton gradient across its plasma membrane under all conditions examined. The mitochondrion of the T. brucei bloodstream form is energized, even though the reactions taking place in it do not result in net ATP synthesis and the Kreb's cycle and the respiratory chain are absent. Glucose is transported across the plasma membrane of T. brucei by a facilitated diffusion carrier, that can transport a wider range of substrates than its mammalian counterparts. Pyruvate exits the cell via a facilitated diffusion transporter as well. Conflicting evidence exists for the mechanism of glucose transport in L. donovani; biochemical evidence suggests proton/glucose symport, while facilitated diffusion is indicated by physiological data.

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Further Evidence for the Existence of a Membrane Potential in Trypanosoma brucei brucei

Cited by 3 publications

References 9 publications

The distribution of permeant ions demonstrates the presence of at least two distinct electrical gradients in bloodstream forms of Trypanosoma brucei

The distribution of permeant ions demonstrates the presence of at least two distinct electrical gradients in bloodstream forms of Trypanosoma brucei

Kinetic study of the plasma-membrane potential in procyclic and bloodstream forms of Trypanosoma brucei brucei using the fluorescent probe bisoxonol

Membrane-related processes and overall energy metabolism inTrypanosoma brucei and other kinetoplastid species

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