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      Phosphocreatine and Creatine Kinase in Energetic Metabolism of the Porcine Carotid Artery

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          Abstract

          Objectives: Magnetization exchange experiments and force analysis were performed on porcine carotid arteries with varied phosphocreatine (PCr) levels. The aim of these experiments was to determine the creatine kinase (CK) kinetics and the role in hypoxic relaxation. Methods: The magnetization exchange techniques used were multisite saturation transfer (MST) and conventional saturation transfer (CST). The two techniques were used because CST assumes a two-site exchange while MST allows one to assume a three-site exchange. Mechanical parameters of tension generation and relaxation were measured to determine the energetic effects on contractility of carotid strips. Results: Measurements of molecular exchange between ATP and PCr found the pseudo first-order rate constant (kf) of 0.17 ± 0.04 s<sup>–1</sup> (PCr → ATP) and k<sub>r</sub> = 0.12 ± 0.03 s<sup>-1</sup> (ATP → PCr) in unstimulated porcine carotid artery. In the carotids, despite increased PCr and K<sup>+</sup> stimulation, no magnetization exchange is observable with MST. This result indicates that the ATPase was less than 0.04 µmol/g/s (below the NMR resolution) while CK was 0.11 µmol/g/s. Creatine-loaded carotids showed no significant differences in force measurements: maximal force, resting tension, and the rate of hypoxia were all unchanged. Conclusions: The flux ratio (flux forward over flux reverse) was 0.94 ± 0.13 which was considered to be indicative of CK being at equilibrium in the resting porcine carotid artery. The rate of the CK reaction is rapid enough to assume a two-site kinetic exchange not limiting energetic supply during hypoxia-induced relaxation.

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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
          : 24-30
          Affiliations
          aDepartment of Biochemistry, University of Oxford, UK; bDepartments of Physiology and Radiology, Michigan State University, East Lansing, Mich, USA
          Article
          159074 J Vasc Res 1995;32:24–30
          10.1159/000159074
          7873707
          © 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: 7
          Categories
          Research Paper

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