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      Cytokine-Mediated Growth Hormone Release from Cultured Ovine Pituitary Cells

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          Abstract

          Previous studies have demonstrated that intravenous lipopolysaccharide (LPS) will increase concentrations of growth hormone (GH). One possible explanation for this may reside in the response of the pituitary to specific cytokines. This study sought to determine the effects of recombinant bovine tumor necrosis factor α (TNF), recombinant ovine (ro) interleukin-1α (IL-1α), roIL-1β, ro interleukin-2 (IL-2), and ro γ-interferon (INT) on GH release from cultured sheep pituitary cells. Sheep were sacrificed and pituitary cells cultured in DMEM with 10% fetal bovine serum for 3 days. On day 4, cells were washed and serum-free DMEM added to cells. IL-1α and IL-1β were used at 0.2, 2 and 20 ng/ml and the remaining cytokines at 2, 20 and 200 ng/ml. Neither IL-2 nor INT had effects on basal or on GH-releasing hormone (GRH)-stimulated GH release. TNF inhibited GRH-stimulated GH release (p < 0.05). Both IL-1α and IL-1β stimulated GH release from cultured pituitary cells at all doses tested (p < 0.01). Neither IL-1α nor IL-1β had an effect on GRH-stimulated GH release. IL-1 effects were inhibited by H-89 (p < 0.05; a protein kinase A inhibitor) and by nifedipine (p < 0.05; a calcium channel blocker). Both of these mechanisms are central signal transduction mechanisms mediating GRH-stimulated GH release. IL-1-stimulated GH release is partially inhibited (p < 0.05) by lipoxygenase pathway blockers. Phorbol myristate acetate downregulation of protein kinase C did not alter IL-1-stimulated GH release. IL-1β increased the content of both GH and GH mRNA in cultured sheep pituitary cells. We conclude that IL-1 produces a strong stimulus to GH release, which is mediated by calcium entry and protein kinase A activation. IL-1 also activates lipoxygenase pathways. This latter pathway as well as calcium entry were shown to mediate LPS stimulation of GH release from cultured pituitary cells. The similarity between IL-1 and LPS signal transduction suggests that LPS may activate pituitary production of IL-1 to produce the stimulus to GH. The lack of inhibitory effects of INT, TNF and IL-2 as opposed to what is seen in the rat may suggest a partial mechanism to explain the different effects of LPS on GH release between sheep and that seen in cattle and rats.

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          Interaction of cyclic AMP- and calcium-dependent mechanisms in the regulation of growth hormone-releasing hormone-stimulated growth hormone release from ovine pituitary cells

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            Author and article information

            Journal
            NEN
            Neuroendocrinology
            10.1159/issn.0028-3835
            Neuroendocrinology
            S. Karger AG
            0028-3835
            1423-0194
            1998
            September 1998
            18 September 1998
            : 68
            : 3
            : 192-200
            Affiliations
            Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Ala., USA
            Article
            54366 Neuroendocrinology 1998;68:192–200
            10.1159/000054366
            9734004
            © 1998 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: 5, Tables: 2, References: 21, Pages: 9
            Categories
            Growth Hormone Regulation

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