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      Thymulin Stimulates Corticotrophin Release and Cyclic Nucleotide Formation in the Rat Anterior Pituitary Gland

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          Abstract

          The neuroendocrine system plays a key role in the regulation of the secretion of the thymic peptide, thymulin, but it remains to be determined whether thymulin exerts reciprocal regulatory actions on the functional activity of the hypothalamo-pituitary axis. In the present study, we have used a well established in vitro preparation to examine the influence of thymulin on cyclic nucleotide formation and hormone secretion by the rat anterior pituitary gland. Thymulin-Zn<sup>2+</sup>(0.5–50 p M) stimulated the release of immmunoreactive corticotrophin (ir-ACTH), producing effects which were maximal at 10 p M (p < 0.01). At the two highest concentrations tested (10 and 50 p M), italso produced small but significant increases in immunoreactive luteinising hormone (ir-LH) release (p < 0.05), but the secretion of immunoreaffive growth hormone (ir-GH) was unaffected by the peptide (p > 0.05) while that of immunoreactive prolactin (ir-PRL) was reduced (p < 0.01). The ACTH responses to thymulin were accompanied by increased cyclic nucleotide formation. Thus, thymulin (0.5–50 p M) raised the cyclic 3′,5′-adenosine monophosphate (cyclic AMP) content of the pituitary tissue (p < 0.01). At high concentrations (10–50 p M), it also increased cyclic 3′,5′-guanosine monophosphate (cyclic GMP; p < 0.01) accumulation, although lower concentrations of the peptide were ineffective in this regard. The increases in ir-ACTH release provoked by thymulin-Zn<sup>2+</sup>(0.5–5.0 p M) were potentiated markedly by rolipram (1µ M; p < 0.01), a selective inhibitor of the cyclic-AMP-specific phosphodiesterase enzyme. By contrast, zaprinast (10µ M), a selective inhibitor of cyclic-GMP-specific phosphodiesterase, attenuated the corticotrophic responses to higher concentrations of the peptide (10 and 50 p M;p < 0.05). Neither rolipram (1µ M) nor zaprinast (10µ M) influenced the release of ir-LH, ir-PRL or ir-GH in the presence or absence of thymulin-Zn<sup>2+</sup>(0.5–50 p M; p > 0.05). The results suggest that thymulin modulates the secretion of ACTH and possibly LH by the anterior pituitary gland and that its actions are associated with increased cyclic nucleotide formation; in addition, it appears to exert an inhibitory influence on ir-PRL release.

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          Author and article information

          Journal
          NIM
          Neuroimmunomodulation
          10.1159/issn.1021-7401
          Neuroimmunomodulation
          S. Karger AG
          1021-7401
          1423-0216
          1997
          1997
          03 December 1997
          : 4
          : 2
          : 62-69
          Affiliations
          Department of Neuroendocrinology, Division of Neuroscience and Psychological Medicine, Imperial College School of Medicine, Charing Cross Hospital, London, UK
          Article
          97322 Neuroimmunomodulation 1997;4:62–69
          10.1159/000097322
          9483196
          7b0a133f-c81b-4698-b573-fc52f4aa7a9b
          © 1997 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.

          History
          Page count
          Pages: 8
          Categories
          Original Paper

          Endocrinology & Diabetes,Neurology,Nutrition & Dietetics,Sexual medicine,Internal medicine,Pharmacology & Pharmaceutical medicine
          Corticotrophin,Thymulin,Phosphodiesterase enzymes,Cyclic nucleotides

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