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

      Further Studies on the Maturation of the Estrogen Negative Feedback on Gonadotropin Release in the Female Rat

      , ,

      Neuroendocrinology

      S. Karger AG

      Sexual development, Females, FSH, LH, Estradiol

      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

          To evaluate estrogen negative feedback in infantile female rats, 9-day-old rats were ovariectomized (OVX) and treated with different doses of estradiol benzoate (Eb, s.c. once daily for 2 days); plasma LH, FSH and estradiol (E<sub>2</sub>) levels were then determined by RIA. The responses of these rats were compared with those of 25-day-old rats subjected to the same experimental procedures. In intact sham-operated controls, plasma FSH was elevated on days 9–13 and low on days 25–29, whereas LH did not change significantly throughout the period studied. OVX at day 9 or 25 increased the levels of both hormones, with the response faster and larger in the older rats. Treatment with Eb was more effective in suppressing the post-castration rise in gonadotropin levels in 27-day-old than in 11-day-old rats. At day 27 plasma E<sub>2</sub> was elevated to pre-castration values by as little as 10 ng of Eb, whereas at day 11 this dose produced plasma E<sub>2</sub> titers even higher than pre-castration values. Plasma E<sub>2</sub> titers were high at 9–13 days of age and low at days 25–29. OVX on day 9 decreased E<sub>2</sub> 2–4 days later to about ½ the initial concentration, whereas adrenalectomy (ADRX) or ADRX-OVX was followed by an almost complete disappearance of the steroid. When E<sub>2</sub> was injected at day 10 in intact rats to elevate plasma E<sub>2</sub>, E<sub>2</sub> remained elevated when measured 3 to 120 min after its injection, but on day 25, 50% of the injected E<sub>2</sub> had disappeared from plasma in 90 min. These results provide additional support for the view that estrogen negative feedback, even though present in infantile rats, is less effective than later in life and hence indicate that high gonadotropin titers observed at days 9–13 in the presence of high E<sub>2</sub> may be caused by the relative ineffectiveness of the feedback at these early ages. The high E<sub>2</sub> titers appear to be caused by an enhanced rate of production of E<sub>2</sub> by the adrenals and ovaries and by a reduced metabolic clearance of the steroid.

          Related collections

          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1975
          1975
          20 March 2008
          : 18
          : 3
          : 242-255
          Affiliations
          Department of Physiology, The University of Texas Health Science Center at Dallas, Southwestern Medical School, Dallas, Tex., and Department of Dairy Science, University of Florida, Gainesville, Fla.
          Article
          122403 Neuroendocrinology 1975;18:242–255
          10.1159/000122403
          1186963
          © 1975 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: 14
          Categories
          Paper

          Comments

          Comment on this article