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      Effect of Protamine on Ion Selectivity of Superficial and Juxtamedullary Proximal Straight Tubules

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          Abstract

          Protamine is known to inhibit cation selectivity of the paracellular shunt pathway in several leaky nephron segments. Ion permeability of the superficial (SF) proximal straight tubules (PST) is selective to Cl<sup>–</sup>, whereas that of the juxtamedullary (JM) PST is selective to Na<sup>+</sup>. Protamine was used to estimate the contribution of the paracellular shunt pathway to ion selectivity in these segments. PSTs were isolated from the kidneys of Japanese white rabbit and microperfused in vitro. The ratio of Na<sup>+</sup> to Cl<sup>–</sup> permeability (P<sub>Na</sub>/P<sub>Cl</sub>) was estimated from the diffusion potential (dV<sub>T</sub>) generated by NaCl gradients. When 300 µg/ml protamine was added to the lumen, P<sub>Na</sub>/P<sub>Cl</sub> was decreased from 0.33 to 0.26 in SF-PST and from 1.80 to 1.29 in JM-PST, respectively, as the results of inhibition of cation selectivity. Addition of 30 U/ml heparin to the lumen, which neutralizes protamine, returned the ratios toward the control levels. Protamine exhibited similar effect on P<sub>Na</sub>/P<sub>Cl</sub> in the presence or the absence of ouabain in the bath, indicating that the observed voltage deflections were independent of the transcellular active transport process. Although P<sub>Na</sub>/P<sub>Cl</sub> was different between SF- and JM-PST, protamine inhibits Na<sup>+</sup> permeability in both segments. Preferential Cl<sup>–</sup> permeability in the SF-PST may be intrinsic to the paracellular route of this segment. The mechanism of this anion selectivity remains to be established.

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          Increase of Urinary Type IV Collagen in Normoalbuminuric Patients with Impaired Glucose Tolerance

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            Author and article information

            Journal
            NEF
            Nephron
            10.1159/issn.1660-8151
            Nephron
            S. Karger AG
            1660-8151
            2235-3186
            1999
            October 1999
            22 September 1999
            : 83
            : 2
            : 154-159
            Affiliations
            Departments of aPharmacology, bNephrology, and cClinical Pharmacology, Jichi Medical School, Tochigi, Japan
            Article
            45493 Nephron 1999;83:154–159
            10.1159/000045493
            10516495
            © 1999 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: 1, References: 22, Pages: 6
            Product
            Self URI (application/pdf): https://www.karger.com/Article/Pdf/45493
            Categories
            Original Paper

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