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      Influence of Parathyroidectomy and Calcium on Rat Renal Function

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          Abstract

          Parathyroid hormone (PTH) has multiple effects on water and electrolyte transport along the nephron. However, the influences of PTH and calcium on the urinary concentration ability are not fully understood. In this study, clearance and microperfusion studies were performed in thyroparathyroidectomized (TPTX) rats either supplemented (TPTX+Ca<sup>2+</sup>) or not with calcium added to the ingested food as CaCl<sub>2</sub> (1.6 g/100 g). Acid-base data and renal functional parameters were measured in TPTX and TPTX+Ca<sup>2+</sup> rats. Additional studies were performed in the isolated inner medullary collecting tubules of intact and TPTX rats to evaluate the osmotic permeability of this segment in the presence of 10<sup>–6</sup> M PTH added to the bath. In these experiments the possible influence of PTH on antidiuretic hormone induced changes of the osmotic permeability in TPTX and TPTX+Ca<sup>2+</sup> rats was also investigated. In the TPTX+Ca<sup>+</sup> group, the glomerular filtration rate increased significantly when compared to the TPTX group (6.04 ± 0.42 vs. 4.88 ± 0.20 ml·min<sup>–1</sup>·kg<sup>–1</sup>; p < 0.05), but the U/P inulin ratio remained lower than control values (30.8 ± 1.48 vs. 54.0 ± 3.5; p < 0.05), which suggests that normal levels of PTH are necessary to maintain the concentrating ability. In a group of TPTX rats, an acute infusion of PTH (0.5 µg·min<sup>–1</sup>·kg<sup>–1</sup>) significantly decreased the urinary flow and increased the renal plasma flow, results that agree with the vasomodulator action of this hormone on the renal vasculature. A significant increase in the fractional K<sup>+</sup> excretion observed in the TPTX+Ca<sup>2+</sup> group as compared with both control and TPTX, groups suggests that the excreted load of Ca<sup>2+</sup> may interfere with tubular K<sup>+</sup> handling in the absence of PTH. PTH (10<sup>–6</sup> M) added to the bath of the isolated inner medullary collecting tubules did not change the osmotic permeability, of intact, TPTX, and TPTX+Ca<sup>2+</sup> rats. Furthermore, it did not modify the antidiuretic hormone induced changes in the osmotic permeability. These results suggest that this segment of the nephron is PTH insensitive as far as water and ion transport are concerned.

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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
          September 1999
          31 August 1999
          : 83
          : 1
          : 59-65
          Affiliations
          Disciplina de Fisiologia Renal e Termometabologia, Universidade Federal de São Paulo, e Laboratório de Pesquisa Básica, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, Brasil
          Article
          45474 Nephron 1999;83:59–65
          10.1159/000045474
          10461037
          © 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: 2, Tables: 5, References: 30, Pages: 7
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          Self URI (application/pdf): https://www.karger.com/Article/Pdf/45474
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          Original Paper

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