NMR‐invisible lactate in blood plasma

Bell, Jimmy D.; Brown, Judith C.; Kubal, Gina; Sadler, Peter J.

doi:10.1016/0014-5793(88)81238-9

Cited by 105 publications

(64 citation statements)

References 25 publications

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“…7) in red blood cells in the presence of DIDS. It is known that resonances of some organic anions such as lactate are often specifically broadened in the 1 H-NMR spectra of blood plasma, and the intensities of their spin±echo peaks are greatly reduced probably because of binding to proteins in human plasma [31]. Tartrate released from Sb(III)-bound form may give rise to a peak that is too broad to be observed in spin±echo spectra probably because of binding to high-molecular-mass ligands (e.g.…”

Section: Discussionmentioning

confidence: 99%

Interaction of antimony tartrate with the tripeptide glutathione

Sun

Yan

Cheng

2000

European Journal of Biochemistry

100

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The tripeptide glutathione (g-l-Glu-l-Cys-Gly, GSH) is thought to play an important role in the biological processing of antimony drugs. We have studied the complexation of the antileishmanial drug potassium antimony(III) tartrate to GSH in both aqueous solution and intact red blood cells by NMR spectroscopy and electrospray ionization mass spectrometry. The deprotonated thiol group of the cysteine residue is shown to be the only binding site for Sb (III), and a complex with the stoichiometry [Sb(GS) 3 ] is formed. The stability constant for [Sb(GS) 3 ] was determined to be log K 25 (I 0.1 m, 298 K) based on a competition reaction between tartrate and GSH at different pH* values. In spite of being highly thermodynamically stable, the complex is kinetically labile. The rate of exchange of GSH between its free and Sb-bound form is pH-dependent, ranging from slow exchange on the 1 H-NMR timescale at low pH (2 s 21 at pH 3.2) to relatively rapid exchange at biological pH (. 440 s 21 ). Such facile exchange may be important in the transport of Sb(III) in various biofluids and tissues in vivo. Our spin±echo 1 H-NMR data show that Sb(III) rapidly entered red blood cell walls and was complexed by intracellular glutathione.Keywords: antimony; glutathione; nuclear magnetic resonance; red blood cells.Leishmaniasis is a parasitic infection caused by various species of the protozoan Leishmania. It remains one of the largest killers in the tropical regions of America, Africa and Asia, with approximately 1.5 billion people at risk and 20 million cases being reported annually. Among the drugs used to treat this condition, several antimony-containing complexes, such as N-methylglucamine antimonate(V) (Glucantimew), sodium stibogluconate (Pentostamw), sodium antimony(III) gluconate (Triostamw) and potassium antimony(III) tartrate (Tartar emeticw), are currently the first choice [1±3], despite their toxicity [4]. Antimony complexes with mannan appear to be promising for further improving the stability and solubility of these drugs [5]. Despite extensive clinical use for several decades, the molecular basis for the selective antileishmanial action of these drugs remains unclear. Furthermore, clinical resistance to these drugs has been increasingly reported in recent years [6±8]. It is generally believed that relatively nontoxic Sb(V) complexes may be prodrugs that could be reduced to the more toxic and active trivalent Sb(III) at or near the site of action (e.g. amastigotes) [9,10].Glutathione (g-l-Glu-l-Cys-Gly, GSH) is a potentially polydentate ligand, and is widely used as a model system for the binding of metal ions by peptides and proteins. It is present in many cells at millimolar concentration and generally is the most abundant nonprotein thiol. In cells, one of its roles is as a substrate for glutathione peroxidase, an enzyme capable of both removing hydrogen peroxide from cells and repairing peroxidatively damaged membranes. It is also involved in metal detoxification, and an ATP-dependent glutathione S-conjugate pump has ...

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Section: Discussionmentioning

confidence: 99%

Interaction of antimony tartrate with the tripeptide glutathione

Sun

Yan

Cheng

2000

European Journal of Biochemistry

100

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“…The ability of 'H NMR to quantitate lactate anion in tissue has been a point of contention recently with the conclusion that not all cellular lactate anion may be NMR visible (3). Contributions from other species resonating at similar chemical shifts (e.g., threonine) complicate the problem of quantitation.…”

Section: Introductionmentioning

confidence: 99%

Fucose in ¹H COSY spectra of plasma membrane fragments shed from human malignant colorectal cells

Lean

Mackinnon

Mountford

1991

Magnetic Resonance in Med

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The methyl-methine cross peak of bound fucose has been assigned in the COSY spectrum of plasma membrane shed from human malignant colorectal cells. This cross peak (1.33-4.27 ppm), which is superimposed on the methyl-methine cross peak of threonine, was assigned following hydrolysis of the sample. Acid hydrolysis led to a 28 +/- 5% reduction in the intensity of the cross peak and the appearance of the alpha and beta forms of fucose. Chemical analysis confirmed the release of free fucose. Lactate anion, which was not perturbed by the hydrolysis, was used as an internal standard.

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“…It has been reported that under some conditions lactate added to the high-molecular-mass fraction of plasma gave 'H-NMR signals that were too broad to detect in either spin-echo or single-pulse spectra (Bell et al, 1988). Similarly, lactate is reported to be 40% invisible in a bovine serum albumin solution (Chatham and Forder, 1995).…”

Section: Discussionmentioning

confidence: 99%

Thermodynamic Significance of the Lactate Gradient

Hockings¹,

Rogers²

1997

European Journal of Biochemistry

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The theory that some bacteria can save energy by an energy-recycling process, in which protons are excreted with metabolic end-products with variable stoichiometry, has been examined by 'H-NMR. A method has been developed that utilises observed differences in the Hahn Tz relaxation of metabolites in the intracellular and extracellular compartments to distinguish and quantify metabolite signals originating from both compartments. It was found that the lactate electrochemical-potential gradient calculated from the fraction of lactate that is sufficiently mobile to contribute to the NMR signal was in exact balance with the proton electrochemical-potential gradient over a wide range of pH values. The conclusion was reached that previous reports of variable stoichiometry were due to 'bound' lactate at high intracellular pH that could neither contribute neither to the NMR signal nor to the lactate electrochemical-potential gradient.Keywords: lactate transport; variable stoichiometry ; Enterococcus ,fuecalis.In 1976 Rottenberg presented a model for H+/metabolite cotransport with pH-dependent variable stoichiometry (Fig. 1). The proton/solute stoichiometry was assumed to vary with the dissociation state of the carrier so that at high external pH the stoichiometry was two and at low external pH the stoichiometry was one. Rottenberg's model formed the basis for the energy-recycling model (Michels et al., 1979), in which end-product efflux may occur with stoichiometries greater than one and thus contribute to the metabolic-energy production during the fermentation process (Rottenberg, 1976;Michels et al., 1979). A number of reports have appeared in the literature in which an apparent end-product efflux with variable stoichiometry has been demonstrated Konings, 1980, 1982;Otto et al., 1980Otto et al., , 1982 Simpson et al., 1983a, b). This model is very attractive as it has been calculated that a stoichiometry of two for H+/lactate efflux would lead to a theoretical energy gain of 50% over bacteria in which the stoichiometry of cotransport was one (Konings, 1985). The decrease in stoichiometry as extracellular pH (pH,,) decreases was said to be essential to prevent the cells from self-poisoning (Konings, 1985) by building up a non-physiologically high intracellular lactate concentration ([lactate],).Despite the attraction of the variable-stoichiometry model, the possibility of internal leaks poses a threat to the model's viability. At intermediate pH values some of the lactate carriers are transporting lactate and one proton, while others are transporting lactate and two protons (Lolkema and Poolman, 1995). Thus, the carrier can act as a proton shuttle and dissipate the protonmotive force (Ap). A futile cycle of protons or solute or both must result as the lactate carrier cycles through the proton- Macnab and Castle, 1987; Axe and Bailey, 1995). The driving force for the translocation of lactate across the cell membrane is the sum of the proton ( A p) and lactate (AF,,,,,,,) electrochemical-potential gradients. When the...

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NMR‐invisible lactate in blood plasma

Cited by 105 publications

References 25 publications

Interaction of antimony tartrate with the tripeptide glutathione

Interaction of antimony tartrate with the tripeptide glutathione

Fucose in ¹H COSY spectra of plasma membrane fragments shed from human malignant colorectal cells

Thermodynamic Significance of the Lactate Gradient

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NMR‐invisible lactate in blood plasma

Cited by 105 publications

References 25 publications

Interaction of antimony tartrate with the tripeptide glutathione

Interaction of antimony tartrate with the tripeptide glutathione

Fucose in 1H COSY spectra of plasma membrane fragments shed from human malignant colorectal cells

Thermodynamic Significance of the Lactate Gradient

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Fucose in ¹H COSY spectra of plasma membrane fragments shed from human malignant colorectal cells