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      Optimal Transport Parameters of the Inner Medullary Collecting Duct in Interaction between Urine Concentrating and Urea Excreting Mechanisms: A Computer Simulation Study

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          Abstract

          Although the accumulation of urea in the renal medulla is essential for the formation of concentrated urine, it is also necessary for the kidney to excrete considerable amounts of urea into the urine as a waste product of protein degradation. Thus, the urine concentrating capacity is attained by the interaction with the efficiency of urea excretion. To seek the best condition for this phenomenon, we developed an objective function for evaluating urea excreting capacity relative to urine concentrating capacity by using a mathematical model consisting of components of the countercurrent multiplication system: the ascending thin limb, capillary network, and inner medullary collecting duct. The values of the objective functions were calculated as three-dimensional functions of transport parameters for the inner medullary collecting duct, including hydraulic conductivity, urea permeability, and reflection coefficient for urea. The results of the computer analysis revealed that the maximum value of the objective function was attained when values for transport parameters of the inner medullary collecting duct corresponded to those experimentally obtained values reported previously. We conclude that the maximum urine concentrating capacity is limited by the efficiency of urea excreting capacity of the kidney, and vice versa.

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          Author and article information

          Journal
          NEF
          Nephron
          10.1159/issn.1660-8151
          Nephron
          S. Karger AG
          1660-8151
          2235-3186
          1996
          1996
          24 December 2008
          : 74
          : 3
          : 600-606
          Affiliations
          aLaboratory for Neural Modeling, Forefront Research Program, Riken, Wako, Saitama, bDepartment of Pharmacology, Jichi Medical School, Tochigi, Japan
          Article
          189459 Nephron 1996;74:600–606
          10.1159/000189459
          8938688
          © 1996 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
          Pages: 7
          Categories
          Original Paper

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