To investigate the factors determining the natriuretic response to furosemide (F) during Na restriction, we performed clearance studies in 7 healthy humans on a daily Na intake of 200 and 20 mmol. The maximum urine flow during water loading (Vmax) and simultaneous F administration was used as index of tubular fluid output from the proximal tubules. The F-induced natriuresis was only moderately reduced during Na restriction (Na excretion on low vs. normal Na intake: 4.28 ± 0.25 vs. 4.94 ± 0.25 mmol/min; p < 0.05). The diminished natriuresis was mainly due to a significant fall in Na delivery to Henle’s loop of 0.51 ± 0.10 mmol/min which was either caused by a decrease in filtered Na load or a rise in fractional proximal reabsorption. Fractional distal Na reabsorption was less suppressible by F during Na restriction, but this contributed relatively little (0.15 ± 0.11 mmol/min) to the total reduction in Na excretion (0.66 ± 0.10 mmol/min). The F-induced increases in uric acid, phosphate, and bicarbonate excretion suggest an additional proximal site of action of F. This was confirmed by a rise in lithium clearance (CLi), another alleged index of tubular fluid delivery from the proximal tubules. However, the magnitude of the rise in CLi to values markedly exceeding Vmax suggest that CLi overestimates tubular fluid delivery to Henle’s loop during F administration.

This content is only available via PDF.
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.