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      Remodelling and Enhanced Myogenic Tone in Cerebral Resistance Arteries Isolated from Genetically Hypertensive Brattleboro Rats

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          Abstract

          In this study, we examined the structural and functional properties of cerebral resistance arteries isolated from normotensive (Di/N), and hypertensive (Di/H), vasopressin-deficient rats. Di/H rats had a significantly higher mean arterial blood pressure (MAP, 159 ± 3 mm Hg) than Di/N rats (125 ± 2 mm Hg). Vessels were set up in a pressure myograph, and the internal diameter and wall thickness were determined at increasing intraluminal pressures under passive (calcium-free) conditions. Arteries were then pressurized to the MAP of the animal, from which they were isolated and fixed with glutaraldehyde, embedded in araldite, sectioned and examined histologically. Under passive conditions, the middle cerebral artery (MCA) from Di/H rats had a smaller internal diameter than the MCA isolated from Di/N rats at all distending pressures. This smaller internal diameter of vessels from hypertensive rats is characteristic of eutrophic inward remodelling, whereby a similar amount of wall material is organized around a smaller lumen, without vascular growth or an alteration in artery distensibility. We have previously shown that similar structural alterations occur in mesenteric resistance arteries isolated from Di/H rats. In the presence of extracellular calcium (1.6 mmol/l), the MCA isolated from Di/H rats had significantly more intrinsic tone than the MCA isolated from Di/N rats in the pressure range of 10–110 mm Hg, although arteries from both strains had a similar myogenic index. The increased intrinsic constriction was a specific enhancement of pressure-induced tone, since responses to the thromboxane mimetic, U46619, were decreased, rather than increased, in the MCA isolated from Di/H rats. Furthermore, it is unlikely that the increased intrinsic tone in arteries isolated from Di/H rats was due to an impaired endothelial function since responses to the endothelium-dependent vasodilator, bradykinin, were enhanced in these vessels compared to arteries isolated from Di/N rats.

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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
          1998
          February 1998
          06 February 1998
          : 35
          : 1
          : 18-26
          Affiliations
          Department of Physiology and Pharmacology, University of Nottingham Medical School, Nottingham, UK
          Article
          25561 J Vasc Res 1998;35:18–26
          10.1159/000025561
          9482692
          © 1998 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: 7, References: 30, Pages: 9
          Categories
          Research Paper

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