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      Receptor Binding and Internalization of a Unique Biologically Active Angiotensin II-Colloidal Gold Conjugate: Morphological Analysis of Angiotensin II Processing in Isolated Vascular Strips

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          Abstract

          It is well recognized that following binding of ligand, many receptors undergo a process of agonist-induced receptor-mediated endocytosis (RME) or internalization. We recently characterized the intracellular pathway and kinetics of angiotensin II (AII)-RME in cultured explant-derived rat aortic vascular smooth muscle cells (VSMCs). To definitively study vascular internalization of AH, however, it is critical to examine AII binding and uptake in intact, differentiated VSM. For the present study, we used a unique, biologically active All-colloidal gold conjugate to qualitatively examine, by transmission electron microscopy, the ultrastructural details of AII binding and internalization in intact VSM. Strips of isolated, cleaned, and denuded rat aortic smooth muscle were incubated with All-gold probe for 2 h at 4° C to allow binding of the complex without simultaneous internalization. After rinsing to remove unbound All-gold, the strips were incubated at 37 °C (5–90 min) to initiate internalization. These studies show that AII initially binds over the entire surface of medial VSMCs. Following binding the AII is internalized via small receptosomes which likely represent clathrin-coated vesicles. By 20 min after internalization, gold particles are evident within large lysosome-like vesicles deep within the VSM. There was no evidence of association of gold particles with the Golgi network at any of the time periods examined. Gold particles were occasionally observed in perinuclear regions after 90 min at 37°C, although this did not appear to represent a typical pattern. AII-gold binding and internalization were selective: control probe (no AII) did not internalize; Losartan potassium (selective AT<sub>1</sub> receptor antagonist) effectively competed for All-gold binding and internalization.

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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
          1994
          1994
          23 September 2008
          : 31
          : 1
          : 10-17
          Affiliations
          Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Va., USA
          Article
          159026 J Vasc Res 1994;31:10–17
          10.1159/000159026
          7903871
          © 1994 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: 8
          Categories
          Research Paper

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