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      Normally Cycling and Latch Bridges in Venous Smooth Muscle

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      Journal of Vascular Research

      S. Karger AG

      Smooth muscle mechanics, Saphenous vein, Length-tension, Force-velocity, Crossbridges

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          Abstract

          We have studied the mechanical properties of the crossbridges of canine saphenous venous smooth muscle during activation by electrical stimulation. A length-tension relationship study showed that at optimal length (1₀) the maximum isometric tension (P₀) developed was 87.9 mN/mm<sup>2</sup>. Resting tension at l<sub>o</sub> was only 6% P₀, which indicates a very compliant muscle. Active tension was observed at muscle lengths greater than 0.3 l<sub>o</sub>. The maximum shortening capacity was 0.65 l<sub>o</sub>. Force-velocity and series elastic characteristics were determined by the method of quick release to a set of load clamps applied during the course of an isometric contraction. The data were fitted by the hyperbolic Hill equation. Estimated maximum shortening velocity at zero load (V₀) an index of the crossbridge cycling rate) was 0.26 l<sub>o</sub>/s which was attained early in the contraction (5 s after the stimulation). A 11.9% decline in V₀ was observed at the plateau of the contraction which occurred at 15 s. The stress (a)-strain (e) curve for the series elastic component could be approximated by the equation a = B[exp(Ae) – 1], where A = 76.51 (1/1₀), B = 2.89 mN/mm<sup>2</sup> at 5 s and A = 61.49 (1/l<sub>o</sub>), B = 1.85 mN/mm<sup>2</sup> at 15 s. Like other smooth muscles, in general, saphenous vein develops considerable isometric tension and has a high shortening capacity but a low shortening velocity. The reduction in shortening velocity that occurs after 5 s in an isometric contraction is probably due to the development of so-called latch bridges.

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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
          1989
          1989
          23 September 2008
          : 26
          : 5
          : 272-279
          Affiliations
          Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Man. Canada
          Article
          158776 Blood Vessels 1989;26:272–279
          10.1159/000158776
          © 1989 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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