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Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pupsNorthern elephant seal (Mirounga angustirostris) pups rely on the oxidation of fat stores as their primary source of energy during their 8- to 12-wk postweaning fast; however, potential endocrine mechanisms involved with this increased fat metabolism have yet to be examined. Therefore, 15 pups were serially blood sampled in the field during the first 7 wk of their postweaning fast to examine the changes in plasma concentrations of cortisol and thyroid hormones (TH), which are involved in fat metabolism in other mammals. Cortisol increased, indicating that it contributed to an increase in lipolysis. Increased total triiodothyronine (tT(3)) and thyroxine (tT(4)) may not reflect increased thyroid gland activity, but rather alterations in hormone metabolism. tT(3)-to-tT(4) ratio decreased, suggesting a decrease in thyroxine (T(4)) deiodination, whereas the negative correlation between total proteins and free T(4) suggests that the increase in free hormone is attributed to a decrease in binding globulins. Changes in TH are most similar to those observed during hibernation than starvation in mammals, suggesting that the metabolic adaptations to natural fasting are more similar to hibernation despite the fact these animals remain active throughout the fasting period.
Document ID
20040112589
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Ortiz, R. M.
(University of California Santa Cruz, California 95064, United States)
Wade, C. E.
Ortiz, C. L.
Date Acquired
August 21, 2013
Publication Date
March 1, 2001
Publication Information
Publication: American journal of physiology. Regulatory, integrative and comparative physiology
Volume: 280
Issue: 3
ISSN: 0363-6119
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: GM 58903-01
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Cardiopulmonary
Non-NASA Center
NASA Center ARC

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