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      Responses of Smooth Muscle to Quick Load Change Studied at High Time Resolution

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          Abstract

          Quick-release and quick-stretch experiments have been performed on preparations of smooth muscle from rat portal vein and rabbit urinary bladder. The low equivalent mass of the isotonic lever (8 mg) implied that inertial oscillations were limited to the first 5–10 msec after the load step. The high time resolution achieved in this way enabled us to separate three components in the length response to a step change in force: (1) an immediate passive elastic recoil, (2) an isotonic velocity transient lasting 50–75 msec and (3) shortening of the contractile element after its full adjustment to the new load. The maximal series elastic recoil was about 10% of the total muscle length in portal vein but only some 3% in urinary bladder. Stiffness of series elasticity increased in proportion to force and was about 3 times higher in bladder than in portal vein at any force level. Force-velocity relations for loads less than P<sub>o</sub> could be fitted to Hill’s equation; V<sub>max</sub> in 4 AC-stimulated portal veins was 0.53 ± 0.03 muscle lengths/sec and in 8 K<sup>+</sup>-activated bladder preparations 0.18 ± 0.01 muscle lengths/sec. Application of loads greater than P<sub>o</sub> produced rates of lengthening greater than expected from an extrapolation of Hill’s hyperbola. The nature of the transient component is discussed in the light of recent studies of force and velocity transients in skeletal muscle.

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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
          978-3-8055-2857-3
          978-3-318-02028-1
          1018-1172
          1423-0135
          1978
          1978
          18 September 2008
          : 15
          : 1-3
          : 65-82
          Affiliations
          Department of Physiology and Biophysics, University of Lund, Lund
          Article
          158154 Blood Vessels 1978;15:65–82
          10.1159/000158154
          © 1978 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: 18
          Categories
          Molecular and Cellular Aspects of Vascular Smooth Muscle in Health and Disease

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