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      Pulsatile and Steady Flow-Induced Calcium Oscillations in Single Cultured Endothelial Cells

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          Abstract

          The influence of flow-imposed shear stress on the intracellular calcium concentration ([Ca<sup>2+</sup>]i) of cultured endothelial cells (ECs) remains incompletely understood. In the present study, we measured [Ca<sup>2+</sup>]i in single bovine aortic ECs, using fluorescence ratiometric image analysis. The effects of several flow patterns were analysed: steady shear stress (5–70 dyn/cm<sup>2</sup>), 1-Hz pulsatile shear stress (nonreversing 40 ± 20 dyn/cm<sup>2</sup>, reversing 20 ± 40 dyn/cm<sup>2</sup>, or purely oscillatory 0 ± 20 dyn/cm<sup>2</sup>), or changing shear stress levels. Under all flow conditions, single-cell analyses revealed flow-induced asynchronous [Ca<sup>2+</sup>]i oscillations, which occurred randomly over the monolayer and which were not seen in the average [Ca<sup>2+</sup>]i signal corresponding to the monolayer response. The number of single-cell [Ca<sup>2+</sup>]i oscillations and the corresponding oscillation frequency rose as the shear stress associated with the steady flow increased: 0.06 ± 0.02 min<sup>–1</sup> at 5 dyn/cm<sup>2</sup>, 0.19 ± 0.03 min<sup>–1</sup> at 20 dyn/cm<sup>2</sup>, and 0.28 ± 0.02 min<sup>–1</sup> at 70 dyn/cm<sup>2</sup> (means ± SD). Also, the number of oscillations was greater for any type of pulsatile flow (0.53 ± 0.07 min<sup>–1</sup> at 40 ± 20 dyn/cm<sup>2</sup>,0.54 ± 0.08 min<sup>–1</sup> at 20 ± 40 dyn/cm<sup>2</sup>, and 0.39 ± 0.07 min<sup>–1</sup> at 0 ± 20 dyn/cm<sup>2</sup>), as compared to any level of steady flow. The most dramatic finding was that purely oscillatory flow induced numerous single-cell [Ca<sup>2+</sup>]i oscillations, yet the average [Ca<sup>2+</sup>]i response for the monolayer did not change. Furthermore, an EC monolayer switched from low to high (or from high to low) steady flow consistently showed an increase (or a decrease) in the number of single-cell [Ca<sup>2+</sup>]i oscillations. These experiments show that ECs respond to different flow conditions by varying single-cell [Ca<sup>2+</sup>]i oscillatory activity. This may have important implications in the endothelium-dependent control of vascular physiology, such as the release of vasoactive substances.

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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
          1996
          1996
          24 September 2008
          : 33
          : 5
          : 360-369
          Affiliations
          School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Ga., Division of Cardiology, University of Washington, Seattle, Wash., USA
          Article
          159164 J Vasc Res 1996;33:360–369
          10.1159/000159164
          8862141
          © 1996 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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