HORMONAL REGULATION OF THYROID-RELATED GENE EXPRESSION IN THE RED DRUM, SCIAENOPS OCELLATUS

Abstract

Event Abstract Back to Event HORMONAL REGULATION OF THYROID-RELATED GENE EXPRESSION IN THE RED DRUM, SCIAENOPS OCELLATUS Richard A. Jones1*, William B. Cohn1, Scott Jaques2 and Duncan S. MacKenzie1 1 Texas A&M University, Biology, United States 2 Endocrine Diagnostic Laboratory of the Texas Veterinary Medical Diagnostics Laboratory, United States Robust daily rhythms of circulating (thyroxine) T4 and a daily cycle of thyrotropin (TSH) expression in the sciaenid fish, the red drum, suggest that circulating thyroid hormones may play a dynamic role in feedback regulation of TSH. If thyroid function is regulated through a 3,5,3’-triiodothyronine (T3) set point, it would be expected that physiological levels of T4 would be more effective in negative feedback on TSH than T3. We found that in vitro pituitary incubation in medium containing 10nM T3 did not significantly alter the expression of either the alpha or beta subunit of TSH but incubation with T4 at 10nM significantly inhibited the expression of TSH-beta. To further examine the differential effects of thyroid hormones we developed an immersion technique to administer physiological doses of T3 and T4 in vivo. Both hormones persist in static tank water for at least 40hrs. Immersion in tank water at 200ng/ml T4 significantly increased plasma T4 by 23.5 ng/ml over control by 40 hours while inhibiting plasma T3 by 2.3 ng/ml below control. Similarly, immersion in 100ng/ml T3 increased plasma T3 by 13.2 ng/ml over control by 22 hours while decreasing plasma T4 by 6.0 ng/ml below control, presumably through inhibition of TSH secretion. Liver expression of type 3 deiodinase was unaffected by T4 but significantly increased by 22hrs of T3 static immersion. These result indicate that T4 negative feedback is a physiological regulator of TSH expression in red drum, but further suggest that hepatic thyroid hormone deactivating pathways are more sensitive to alterations in circulating T3 than T4, supporting a role for a peripheral T3 set point in regulating thyroid hormone delivery to target tissues. Keywords: deiodinase, Feedback, Immersion, T3, T4, thyroid, Thyrotropin, TSH Conference: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology, Ann Arbor, United States, 13 Jul - 16 Jul, 2011. Presentation Type: Poster Topic: Biological rhythms Citation: Jones RA, Cohn WB, Jaques S and MacKenzie DS (2011). HORMONAL REGULATION OF THYROID-RELATED GENE EXPRESSION IN THE RED DRUM, SCIAENOPS OCELLATUS. Front. Endocrinol. Conference Abstract: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology. doi: 10.3389/conf.fendo.2011.04.00148 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 20 Jul 2011; Published Online: 09 Aug 2011. * Correspondence: Mr. Richard A Jones, Texas A&M University, Biology, College Station, Texas, 77843, United States, rajones@mail.bio.tamu.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Richard A Jones William B Cohn Scott Jaques Duncan S MacKenzie Google Richard A Jones William B Cohn Scott Jaques Duncan S MacKenzie Google Scholar Richard A Jones William B Cohn Scott Jaques Duncan S MacKenzie PubMed Richard A Jones William B Cohn Scott Jaques Duncan S MacKenzie Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.