+1 Recommend
1 collections
      • Record: found
      • Abstract: found
      • Article: found

      Neuroeffector Function of Isolated Portal Vein from Spontaneously Hypertensive and Wistar-Kyoto Rats: Dependence on External Calcium Concentration

      Read this article at

          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.


          The calcium dependence of the vascular neuroeffector function has been studied in the portal vein of spontaneously hypertensive Okamoto rats (SHR) and Wistar-Kyoto rats (WKY). The noradrenaline (NA) sensitivity of veins of both species, expressed in terms of ED<sub>50</sub>, was decreased to the same extent in relation to the reduction in Ca<sup>2+</sup> ion concentration below 2.5 mM. The responses to individual NA concentrations at subnormal Ca<sup>2+</sup> concentrations were better maintained, however, in portal veins from SHR than from WKY, indicating that the excitation contraction coupling mechanism is less dependent on external Ca<sup>2+</sup> concentrations in the portal vein from SHR than from WKY. In both strains of rats the spontaneous myogenic activity of the vessel was depressed in low Ca<sup>2+</sup> concentrations to a greater extent than responses to nerve stimulation, which, in turn, were more reduced than the excitatory responses to exogenous NA or acetylcholine (ACh). Transmitter release (fractional overflow of <sup>3</sup>H-NA/impulse) was less dependent on Ca<sup>2+</sup> concentrations than the contractile nerve stimulation response. The persistance of all responses in reduced Ca<sup>2+</sup> concentrations was significantly greater in the portal vein of SHR. It is concluded that the phasic, spontaneously active smooth muscle of the rat portal vein is highly dependent on the external calcium concentration and that various induced responses persist to a varying degree in reduced Ca<sup>2+</sup> concentrations. It is suggested that this is due to interference with electromechanical coupling as well as myogenic spread of activation. Induced responses of the portal vein from SHR are, in general, less affected by decreased Ca<sup>2+</sup> concentrations than the WKY portal vein, indicating an altered vascular smooth muscle excitation-contraction coupling mechanism in spontaneous hypertension. Possibly an increased efficiency of the coupling mechanism may contribute to augment vascular responses in the development of hypertension and promote structural vascular changes.

          Related collections

          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          19 September 2008
          : 18
          : 3
          : 89-99
          Department of Physiology, University of Göteborg, Göteborg, and Department of Pharmacology, AB Hassle, Molndal, Sweden; The Alton Ochsner Medical Foundation, New Orleans, La., USA
          158341 Blood Vessels 1981;18:89–99
          © 1981 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: 11
          Research Paper


          Comment on this article