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      Temporal Aspects of Ca 2+ and Myosin Phosphorylation during Myogenic and Norepinephrine-Induced Arteriolar Constriction

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          Abstract

          Previous studies demonstrated that maintenance of steady-state myogenic tone requires Ca<sup>2+</sup>-dependent myosin phosphorylation. The present studies furthered these observations by examining temporal relationships among Ca<sup>2+</sup>, myosin phosphorylation and vessel diameter during acute increases in intraluminal pressure and norepinephrine stimulation. Rat cremaster muscle arterioles were cannulated and loaded with the Ca<sup>2+</sup>-sensitive indicator fura-2. The extent of myosin phosphorylation was measured using two-dimensional gel electrophoresis. Acute increases in intraluminal pressure caused a biphasic increase in intracellular Ca<sup>2+</sup> ([Ca<sup>2+</sup>]<sub>i</sub>), characterized by a transient peak followed by a decline to a steady-state level which remained significantly higher than control values. Peak [Ca<sup>2+</sup>]<sub>i</sub> was significantly related to vessel distension and increased with the change in wall tension. Increased intraluminal pressure resulted in a monophasic increase in myosin phosphorylation that was significantly correlated with instantaneous wall tension. In general, norepinephrine induced larger [Ca<sup>2+</sup>]<sub>i</sub> transients and a biphasic myosin phosphorylation pattern. The results demonstrate: (a) major roles for Ca<sup>2+</sup> and myosin phosphorylation in arteriolar myogenic and norepinephrine-induced responses; (b) that changes in Ca<sup>2+</sup> and phosphorylation during a myogenic response are related to changes in wall tension, and (c) differences in Ca<sup>2+</sup> and phosphorylation patterns between the two modes of contraction reflect possible differences in underlying signaling mechanisms. The data further emphasize that spontaneous arteriolar tone represents a state of maintained smooth muscle activation that requires increases in [Ca<sup>2+</sup>]<sub>i</sub> and myosin light-chain phosphorylation.

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          Homogeneous catalytic hydrogenation of supercritical carbon dioxide

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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
            2000
            December 2000
            10 January 2001
            : 37
            : 6
            : 556-567
            Affiliations
            Departments of aPhysiology and bPharmacology, Eastern Virginia Medical School, Norfolk, Va., USA; cDepartment of Human Biology and Movement Science, RMIT University, Bundoora, Australia
            Article
            54089 J Vasc Res 2000;37:556–567
            10.1159/000054089
            11146410
            © 2000 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: 9, Tables: 1, References: 28, Pages: 12
            Categories
            Research Paper

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