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      Characteristics of the Norepinephrine-Sensitive Ca 2+ Store in Vascular Smooth Muscle

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          Abstract

          A comparison was made between the properties of the norepinephrine- and caffeine-sensitive Ca<sup>2+</sup> store in both intact and skinned smooth muscle of the rabbit mesenteric artery. After a first application of 10<sup>-5</sup> M norepinephrine, reapplication of norepinephrine did not induce a second contraction in Ca<sup>2+</sup>-free medium. However, following this sequence 25 m M caffeine still induced a large contraction. The rates of Ca<sup>2+</sup> leakage and Ca<sup>2+</sup> filling of the norepinephrine-sensitive store were much faster than those of the caffeine-sensitive one. The amplitude of the norepinephrine-induced contraction in Ca<sup>2+</sup>-free medium also depended on the amount of Ca<sup>2+</sup> present in the caffeine-sensitive store. In the saponin-treated skinned muscle caffeine induced a Ca<sup>2+</sup> release only after loading with Ca<sup>2+</sup>, whereas norepinephrine was unable to induce Ca<sup>2+</sup> release in the skinned preparation even after loading with Ca<sup>2+</sup>. The release of Ca<sup>2+</sup> from the caffeine-sensitive store could be activated by Ca<sup>2+</sup> itself when the skinned muscle was loaded with Ca<sup>2+</sup> above 10<sup>-6</sup> M. These results suggest that the norepinephrine-sensitive Ca<sup>2+</sup> store is distinct from a large fraction of the caffeine-sensitive one, and that the norepinephrine-sensitive store is close to the cell membrane. In vascular smooth muscle, under physiological conditions, Ca<sup>2+</sup> released from the norepinephrine-sensitive store by norepinephrine may induce Ca<sup>2+</sup> release from the caffeine-sensitive Ca<sup>2+</sup> store which may be comprised of the sarcoplasmic reticulum.

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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
          1984
          1984
          23 September 2008
          : 21
          : 1
          : 43-52
          Affiliations
          Department of Pharmacology, University of Miami School of Medicine, Miami, Fla., USA
          Article
          158493 Blood Vessels 1984;21:43–52
          10.1159/000158493
          © 1984 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: 10
          Categories
          Research Paper

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