In previous microperfusion studies in the rat, increasing luminal fluid magnesium concentration from 1.5 to 6.0 mEq/1 resulted in a 62% fall in proximal and a 74% fall in distal tubular osmotic water permeability. To determine whether this reduction in rat proximal tubular osmotic water permeability produced osmotic dysequilibrium between proximal tubular fluid and plasma, proximal (TF/P)osm were measured during isotonic saline and magnesium chloride infusion. In 11 rats, proximal (TF/P)osm was 0.99 ± 0.01 during isotonic saline and 0.98 ± 0.01 during magnesium chloride infusion; plasma magnesium concentration increased from 1.76 ± 0.12 to 6.03 ± 0.30 mEq/1. The effect of magnesium on the ability of hydropenic anti-diuretic rats and dogs to reabsorb free water was examined during hypertonic mannitol and saline diuresis. In the rat free water reabsorption was not affected by hypermagnesemia. In the dog hypermagnesemia caused a reduction in free water reabsorption at low levels of solute excretion and formation of a urine hypotonic to plasma at high levels of solute excretion. The reduction in rat proximal and distal tubule osmotic water permeability is not sufficient to affect osmotic equilibration across these tubular segments. Free water reabsorption, reflecting solute reabsorption in the ascending limb of Henle’s loop, is decreased by magnesium in the dog but not in the rat.

Keywords:
Magnesium, Osmotic water permeability, Free water reabsorption, Urinary concentrating ability
This content is only available via PDF.
© 1978 S. Karger AG, Basel
1978
Copyright / Drug Dosage / Disclaimer
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.
You do not currently have access to this content.