PREPARING TO HIBERNATE IN A DEEP FREEZE: ADRENAL ANDROGEN PRODUCTION IN SUMMER LINKED TO ENVIRONMENTAL SEVERITY IN WINTER IN ARCTIC GROUND SQUIRRELS

Abstract

Event Abstract Back to Event PREPARING TO HIBERNATE IN A DEEP FREEZE: ADRENAL ANDROGEN PRODUCTION IN SUMMER LINKED TO ENVIRONMENTAL SEVERITY IN WINTER IN ARCTIC GROUND SQUIRRELS Rudy Boonstra1*, Adrian Bradley1, 2 and Brendan Delehanty1 1 University of Toronto Scarborough, Biological Sciences, Canada 2 University of Queensland,, School of Biomedical Sciences, Australia At high latitudes, evolutionary adaptations for winter focus on those that maximize survival, with hibernation being a major one used by many smaller mammals. Typically, mammalian hibernators overwinter in sites that are ≥ 0 °C. In the arctic, such sites do not exist. Lipid, the normal fuel of most hibernators, may not provide sufficient glucose needed by certain tissues to permit survival, with muscle breakdown being required. Critical to enhancing muscle stores are high concentrations of anabolic androgens at a time when the gonads are inactive. We compare arctic ground squirrels (AGS) from the Arctic and Columbian ground squirrel (CGS) from Alberta. In males, changes in testes mass over the active season were similar in AGS and CGS, being at a maximum prior to breeding, declining rapidly during the breeding period and, by late summer, being <10% of that at emergence. In contrast, during the breeding and pre-hibernation periods, levels in AGS were 6-10 and 20-25 times, respectively, those of CGS. From the breeding to the pre-hibernation periods, levels declined 41% in AGS, but 86% in CGS. In female AGS, androgen levels were high throughout the active season and, prior to hibernation, were 24 times those in female CGS. Androgen levels in both female and male AGS, decreased >10% in response to dexamethasone and increased >18% in response ACTH. These results implicate the adrenals as the source of the androgens. In male AGS, GnRH had no effect on androgen levels, whereas ACTH stimulated them by > 40%, both before and after gonadectomy. Adrenalectomy caused levels to fall by 80%. Thus, the adrenals, not the testes, are the source of the AGS androgens. We conclude that pre-hibernating AGS have evolved a solution seen in no other known mammal: exploiting the benefits of high adrenal androgen levels in nonbreeding animals to build muscle that is then catabolized overwinter. The unknown is how they have mitigated the costs of these steroids. (supported by NSERC grant to RB, Univ. Queensland grant to AJB, DINA grant to BD) Keywords: adrenal steroids, anabolic steroids, arctic climate, Hibernation, muscle anabolism and catabolism, seasonal reproductive status 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: Oral Presentation Topic: Environmental endocrinology Citation: Boonstra R, Bradley A and Delehanty B (2011). PREPARING TO HIBERNATE IN A DEEP FREEZE: ADRENAL ANDROGEN PRODUCTION IN SUMMER LINKED TO ENVIRONMENTAL SEVERITY IN WINTER IN ARCTIC GROUND SQUIRRELS. Front. Endocrinol. Conference Abstract: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology. doi: 10.3389/conf.fendo.2011.04.00006 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: 11 Jul 2011; Published Online: 09 Aug 2011. * Correspondence: Dr. Rudy Boonstra, University of Toronto Scarborough, Biological Sciences, Toronto, Ontario, M1C 1A4, Canada, boonstra@utsc.utoronto.ca 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 Rudy Boonstra Adrian Bradley Brendan Delehanty Google Rudy Boonstra Adrian Bradley Brendan Delehanty Google Scholar Rudy Boonstra Adrian Bradley Brendan Delehanty PubMed Rudy Boonstra Adrian Bradley Brendan Delehanty 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.