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      Influence of Photoinhibition on the Morphology and Function of Pituitary Lactotropes in Male Golden Hamsters

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          Abstract

          Inhibition of prolactin (PRL) secretion has been previously shown in pituitaries from male and female hamsters exposed to short photoperiods. The purpose of the present study was to analyze the possible quantitative immunohistochemical and ultrastructural changes of PRL cells in male golden hamsters undergoing regression and spontaneous recrudescence, correlating the morphological findings with circulating PRL levels. Thus, adult male golden hamsters were exposed for 8, 16, 22 and 28 weeks to either short photoperiods (SP: 6 h light, 18 h darkness) or long photoperiods (LP: 14 h light, 10 h darkness). Pituitaries were processed for both light and electron microscopy, and serum levels of PRL were assessed by radioimmunoassay (RIA). Volume density (VD = cell area/reference area) and cell density (CD = number of cells/reference area) of lactotropes were measured with an image analysis system (Imaging Technology, Software Optimas 5.2). One hundred lactotropes were recorded for measuring several ultrastructural parameters. When analyzing the lactrotrope cell population from animals submitted to SP, the VD and CD were found to be significantly (p < 0.05) diminished with respect to those of the groups submitted to LP at weeks 8, 16 and 22. However, at week 28 a spontaneous recrudescence appeared. The lactotropes from animals submitted to LP for 8, 16, 22 and 28 weeks exhibited numerous large electrondense secretory granules. The rough endoplasmic reticulum (RER) presented some flat cisternae and numerous free ribosomes. Animals submitted to SP for 8 weeks showed a number of medium and large secretory granules, and the RER exhibited mainly numerous free ribosomes. In those animals submitted to SP for 16 and 22 weeks, lactotropes were found smaller and showed small and medium-sized secretory granules decreased in number. The Golgi complex exhibited some immature granules and dilated cisternae, while the RER did not present differences with respect to the 8-week SP group. The hamsters submitted to SP for 28 weeks presented medium and large secretory granules, and the RER exhibited dilated irregular cisternae. The ultrastructural morphometric parameters showed a decrease (p < 0.05) in the number of secretory granules and exocytotic profiles, as well as a diminution (p < 0.05) in the areas of Golgi complex, RER, secretory granules, and individual mean area of secretory granule during the 16 and 22 weeks of SP. Serum PRL levels were severely reduced under SP. This decrease was greater at 16 weeks than at 8 weeks of exposure. When hamsters were kept for 22 weeks under SP, PRL levels started their recovery. Thus, at the end of the experiment, the PRL values returned to near those of LP group. In summary, we found quantitative immunohistochemical and ultrastructural, as well as biochemical changes that suggest an inhibition of synthesis, storage and release of PRL in male golden hamsters submitted to SP, with a spontaneous recrudescence appearing at the end of the study.

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          Dopamine inhibition of prolactin release but not synthesis in the male syrian hamster: In vitro studies

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            Author and article information

            Journal
            NEN
            Neuroendocrinology
            10.1159/issn.0028-3835
            Neuroendocrinology
            S. Karger AG
            0028-3835
            1423-0194
            2002
            May 2002
            29 April 2002
            : 75
            : 5
            : 316-325
            Affiliations
            aCátedra de Histología-Embriología ‘B’, Facultad de Ciencias Médicas, UNLP, Comisión de Investigaciones Científicas Buenos Aires (CICBA); bServicio Central de Microscopía Electrónica, Facultad de Ciencias Veterinarias, UNLP; cCátedra de Endocrinología, Facultad de Ciencias Exactas, UNLP, e dInstituto de Biología y Medicina Experimental, Buenos Aires, Argentina
            Article
            57341 Neuroendocrinology 2002;75:316–325
            10.1159/000057341
            12006785
            © 2002 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: 9, Tables: 2, References: 32, Pages: 10
            Categories
            Neural Regulation of Reproductive Hormones

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