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      Extraction of Uraemic Toxins with Activated Carbon Restores the Functional Properties of Albumin

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          Background: Previous work has demonstrated that a partial normalization of the conformation of albumin from uraemic plasma and a substantial restoration of its binding abilities can be achieved by extraction with activated charcoal. This is best achieved at pH 3, but exposure of whole plasma to this low pH leads to the loss of some essential components. Methods: The melting curves and ligand-binding abilities of uraemic albumin have been investigated after extraction with a new generation of activated carbon at three pH values (7.2, 3.0 and 5.08). Results: Albumin isolated from uraemic plasma had a characteristically increased melting temperature because of bound ligands. Extraction of uraemic plasma at pH 7.2, 5.08 and 3.0 induced low-temperature shifts of albumin thermo-adsorption maximum T<sub>1</sub> of 1.4, 3.8, 2.4°C and T<sub>2</sub> of 0.8, 3.9 and 1.2°C, respectively. Flow microcalorimetry data demonstrated a decrease in the ability of uraemic albumin to bind octanoate, phenol red, salicylic acid, warfarin and diazepam. Purification of uraemic plasma at pH 5.08 completely restored the binding affinity of albumin for all the marker ligands. Conclusions: Highly efficient activated carbons, with clinically feasible acidification of plasma, can remove strongly albumin-bound uraemic toxins. Investigation of the melting curve of the isolated albumin is a new biophysical way to monitor both its molecular condition and the extent of removal of protein-bound toxins by dialysis. The melting curve provides new qualitative and quantitative information about albumin in an analogous way to an electrocardiogram and the heart.

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          Most cited references 8

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          Uremic Toxicity: Urea and Beyond

           Thomas Depner (2001)
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            Contributions of hippurate, indoxyl sulfate, and o-hydroxyhippurate to impaired ligand binding by plasma in azotemic humans.

            We have evaluated pH, chloride, calcium and several endogenous aromatic acids as possible causes of the impaired binding of drugs by plasma albumin in renal failure. Changes in pH, chloride and calcium over the range found in renal failure had minimal or no effects on the binding of [14C]salicylate, a model probe which binds to both of the major drug-binding loci of human albumin. Hippurate and indoxyl sulfate were weak inhibitors of binding by normal plasma. Ortho-hydroxy-hippurate was undetectable or minimally elevated, except among patients with elevated plasma salicylate concentration. Although plasma hippurate and indoxyl sulfate concentrations were elevated markedly in patients with renal failure, inhibition of salicylate binding was significantly correlated only with the concentration of indoxyl sulfate. Addition of hippurate and indoxyl sulfate separately and together to normal plasma showed that these ligands could account for only 15% of the impaired binding of salicylate by azotemic plasma. The retained solutes which account for most of this binding defect remain to be identified. This uremic disorder (and perhaps others) is due not to a single chemical but to the additive effect of a family of chemicals.
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              Protein binding of drugs in uremic and normal serum: The role of endogenous binding inhibitors


                Author and article information

                Nephron Physiol
                Nephron Physiology
                S. Karger AG
                September 2003
                29 September 2003
                : 95
                : 1
                : p10-p18
                aSection of Artificial Organs, Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology of The National Academy of Sciences, Kiev, Ukraine, and bDepartment of Pharmacology and Therapeutics, University of Liverpool, Liverpool, UK
                73024 Nephron Physiol 2003;95:p10–p18
                © 2003 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 3, Tables: 3, References: 37, Pages: 1
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/73024
                Original Paper

                Cardiovascular Medicine, Nephrology

                Uraemia, Human albumin, Activated carbon, Melting curve


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