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      Paradoxical Effects of Isothiocyanate Analog of Tolazoline on Rat Aorta and Human Platelets

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          Abstract

          The isothiocyanate analog (IBI) of tolazoline produced contraction of the rat aortic strip, with an ED<sub>50</sub> value of 1.63 × 10<sup>–5</sup> M. The maximum contraction of the analog was nearly equal to that of tolazoline or phenylephrine. At 27 °C the tissue reactivity of phenylephrine and IBI was similar. When compared at equiactive concentrations, the total duration of contraction of IBI was three times longer than that of tolazoline. Thus, the longer duration of action of IBI may be attributed to the S=C=N group substitution of the molecule. IBI at 10<sup>-6</sup> M shifted the dose-response curve of phenylephrine to the right with reduction in maxima. Phentolamine and other α<sub>1</sub>or α<sub>2</sub> adrenoceptor blockers failed to block the responses of IBI in aorta, whereas verapamil or nifedipine blocked the response significantly. It appears that IBI is acting through calcium-channel-sensitive or calcium-receptor-related mechanism(s). In aspirin-treated platelets from human plasma, a distinct phase of aggregation induced by epinephrine can be blocked by IBI with KB of 2 × 10<sup>–5</sup> M. This indicates a small but selective α<sub>2</sub> related action of IBI. The aggregation induced by ADP or second component of aggregation induced by epinephrine were also blocked by IBI at concentrations comparable to that of the 012-adrenoceptor-mediated response. This indicates a lack of specificity of IBI in differentiating various phases of aggregation. Therefore, as compared to tolazoline, IBI presents an interesting paradox in its interaction with various receptors or mechanisms in the vascular tissue and platelets.

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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
          1989
          1989
          23 September 2008
          : 26
          : 6
          : 335-346
          Affiliations
          Divisions of Pharmacology and Medicinal Chemistry, College of Pharmacy, Lloyd M. Parks Hall, The Ohio State University, Columbus, Ohio, USA
          Article
          158784 Blood Vessels 1989;26:335–346
          10.1159/000158784
          © 1989 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: 12
          Categories
          Research Paper

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