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      Magnitude of Flow-Induced Contraction and Associated Calcium Influx in the Rabbit Facial Vein Is Dependent upon the Level of Extracellular Sodium

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          Abstract

          Intraluminal flow can cause both dilation or constriction of small arteries, depending on the level of tone. Both responses are specifically modulated in the same way by small changes in extracellular Na<sup>+</sup> ([Na<sup>+</sup>]<sub>e</sub>). We have investigated the effect of changes in [Na<sup>+</sup>]<sub>e</sub> on the level of contraction induced by a standard flow of physiological salt solution in ring of segments of the rabbit facial vein and on the associated <sup>45</sup>Ca<sup>2+</sup> influx and net uptake. Decreasing [Na<sup>+</sup>]<sub>e</sub> by 20% reduced the response to flow by 58%, and increasing it by 20% augmented the flow response by the same extent. There is a linear relationship between the level of the flow-induced contraction and [Na<sup>+</sup>]<sub>e</sub> over the range 120-180 m M. An alteration in [Na<sup>+</sup>]<sub>e</sub> of 10 m M corresponds to a 20% change in flow-induced contraction. This relationship is quantitatively the same as that previously reported for the rabbit ear resistance artery [10]. Histamine (1 µ M) induced tone was not affected by changes in [Na<sup>+</sup>]<sub>e</sub> within the range 75-180 m M. <sup>45</sup>Ca<sup>2+</sup> influx and net uptake per unit force developed in response to flow were unaffected by these changes in [Na<sup>+</sup>]<sub>e</sub>. The flow-induced contraction of the vein was selectively, in comparison to that due to histamine, attenuated by amiloride, methyl-isobutyl-amiloride and monensin. It is argued that the observation that flow-induced contraction, caused by small alterations in extracellular sodium concentration, is not associated with changes in calcium uptake per unit force is consistent with an extracellular flow sensor. The similarities of the effects of sodium concentration change and amiloride, methyl-isobutyl-amiloride and monensin in the rabbit facial vein to what has been previously found in the resistance branch of the rabbit ear artery suggest that the flow-sensitive mechanism may be similar in the two vessels.

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          Author and article information

          Journal
          JVR
          J Vasc Res
          10.1159/issn.1018-1172
          Journal of Vascular Research
          S. Karger AG
          1018-1172
          1423-0135
          1995
          1995
          24 September 2008
          : 32
          : 1
          : 41-48
          Affiliations
          Department of Pharmacology and Vermont Center for Vascular Research, University of Vermont, College of Medicine, Burlington, Vt., USA
          Article
          159076 J Vasc Res 1995;32:41–48
          10.1159/000159076
          7873709
          © 1995 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: 8
          Categories
          Research Paper

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