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      Time of Day-Dependent Effects of Thyroliberin and Thyrotropin on Thymocyte Proliferation in Rats

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      Neuroimmunomodulation

      S. Karger AG

      Thyrotropin, Thyroliberin, Thymocytes, Cell proliferation, Chronobiology

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          Abstract

          Our earlier studies have shown that thyroliberin (TRH) as well as thyrotropin (TSH) enhanced thymus cell proliferation. The aim of the present study was to investigate whether the effects of TRH and TSH on thymocyte proliferation depend on time of day. A single subcutaneous injection of TRH (25 μg/animal) or TSH (3 IU/animal) was made at 9:00 h (1 h after light onset) or at 18:00 h (10 h after light onset) in 3-month-old male Wistar rats. The animals were killed 24 h later. The proliferation of thymocytes was assessed by incorporation of bromodeoxyuridine into cell nuclei. Thymocyte proliferation was significantly increased by TSH administration at 9:00 h, whereas treatment given at 18:00 h was ineffective. TRH enhanced the proliferation when injected at 9:00 h, but had an inhibitory effect when administered at 18:00 h. These data indicate that the effects of TRH and TSH on thymocyte proliferation are dependent on time of day.

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          Most cited references 1

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          The involvement of pineal gland and melatonin in immunity and aging. I. Thymus-mediated, immunoreconstituting and antiviral activity of thyrotropin-releasing hormone.

          Circadian, continued treatment with melatonin during the dark cycle produces changes in the blood level of thyroid hormones in aging mice. Thyroid-stimulating hormone (TSH) and thyrotropin-releasing hormone (TRH) antagonize the involution of the thymus produced by prednisolone. This effect of TRH does not seem thyroid dependent. TRH restores antibody production in non-responder athymic nude mice but does not exert this effect in neonatally thymectomized mice. Moreover, this activity does not correlate with thyroxine levels. TRH exerts a powerful protective effect in mice challenged with encephalomyocarditis (EMC) virus. Presumably pineal melatonin exerts its varied regulatory functions via hypothalamic TRH.
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            Author and article information

            Journal
            NIM
            Neuroimmunomodulation
            10.1159/issn.1021-7401
            Neuroimmunomodulation
            S. Karger AG
            1021-7401
            1423-0216
            2000
            February 1999
            18 February 2000
            : 7
            : 2
            : 89-91
            Affiliations
            Department of Experimental Endocrinology and Hormone Diagnostics, Institute of Endocrinology, Medical University of Lodz, Poland
            Article
            26425 Neuroimmunomodulation 2000;7:89–91
            10.1159/000026425
            10686518
            © 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: 2, References: 21, Pages: 3
            Categories
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