0
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found

      Thyroid Hormone Regulation of TRH mRNA Levels in Rat Paraventricular Nucleus of the Hypothalamus Changes during Ontogeny

      , ,

      Neuroendocrinology

      S. Karger AG

      Hypothalamus, Regulation, Ontogeny, TRH, Paraventricular nucleus, Thyroid hormone

      Read this article at

      ScienceOpenPublisherPubMed
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          The changing roles of the hypothalamus and pituitary in regulating thyroid hormone levels in the rat during ontogeny has not been fully elucidated. It has been reported that endogenous TRH begins to stimulate TSH secretion at 5–8 days after birth but that the pituitary responds to hypothyroidism during late gestation. To determine the onset and extent of TRH response to low thyroid hormone levels during ontogeny, normal and hypothyroid rats treated with methimazole for 7 days were sacrificed at 16 days gestation (E16), 20 days gestation (E20), 7, 21 and 56 days after birth (n = 5/study group). Plasma hormones were assayed from pregnant mothers, pups (pooled) and adults. Levels of TRH mRNA were measured in the paraventricular nuclei (PVN) by in situ hybridization histochemistry. A labeled 48-base cDNA oligonucleotide for TRH was hybridized with brain slices (n = 6/animal) in the region of the medial parvocellular division of the PVN of the hypothalamus and the signal was quantitated by digitized computer analysis. Plasma-free T4 levels decreased and plasma TSH levels increased in the animals treated with methimazole as compared to the euthyroid controls. TRH mRNA was detected in the PVN at E16 after brain slices were dipped in emulsion and granules observed by dark-field microscopy. In the euthyroid animals, TRH mRNA increased from E20 (150 ± 9 OD units) to 7 days (222 ± 5 OD units) and remained unchanged at 21 days (252 ± 27 OD units) and 56 days (244 ± 6 OD units). The hypothyroid rats as compared to age-matched controls, had TRH mRNA levels that were unchanged at E16 and E20 and increased to 121% at 7 days (269 ± 9 0D units; p < 0.001), 176% at 21 days (461 ± 26 OD units; p < 0.001), and 225% at 56 days (545 ± 20 OD units; p < 0.001). In summary, TRH mRNA was present in the PVN at E16 and increased until 7 days after birth. TRH mRNA was not altered with hypothyroidism until after E20 and prior to or on the 7th day after birth when levels increased in response to low thyroid hormone levels. Thus, the ontogeny of the regulation of thyroid hormone feedback on TRH mRNA levels and of TSH secretion by endogenous TRH may be temporally associated suggesting an important role of PVN maturation in the development of the thyroid axis.

          Related collections

          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1990
          1990
          03 April 2008
          : 52
          : 3
          : 262-267
          Affiliations
          Molecular, Cellular, and Nutritional Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Laboratory of Cell Biology, National Institute of Mental Health, National Institutes of Health, Bethesda, Md.; Georgetown University Hospital, Washington, D.C, USA
          Article
          125596 Neuroendocrinology 1990;52:262–267
          10.1159/000125596
          2120608
          © 1990 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: 6
          Categories
          Original Paper

          Comments

          Comment on this article