Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pups

Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pups Abstract Northern 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. fat metabolism food deprivation leptin marine mammals Footnotes This research was supported by National Institutes of Health Minority Access to Research Careers Grant GM 58903–01 (C. L. Ortiz), National Aeronautics and Space Administration (NASA) Graduate Student Research Program NGT-2–52230 (R. M. Ortiz), and NASA Grants 121–10–50 and 121–40–10 (C. E. Wade). This research was conducted in partial fulfillment of the requirements for the doctorate degree in biology for R. M. Ortiz. Research was conducted under National Marine Fisheries Service marine mammal permit #836 to C. L. Ortiz and UCSC Chancellor's Animal Research Committee permit Orti89.08 to C. L. Ortiz and R. M. Ortiz. Address for reprint requests and other correspondence: R. M. Ortiz (E-mail: rortiz@mail.arc.nasa.gov ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2001 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Regulatory, Integrative and Comparative Physiology The American Physiological Society

Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pups

Loading next page...
 
/lp/the-american-physiological-society/effects-of-prolonged-fasting-on-plasma-cortisol-and-th-in-postweaned-NP9gU0pVZ2
Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
0363-6119
eISSN
1522-1490
Publisher site
See Article on Publisher Site

Abstract

Abstract Northern 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. fat metabolism food deprivation leptin marine mammals Footnotes This research was supported by National Institutes of Health Minority Access to Research Careers Grant GM 58903–01 (C. L. Ortiz), National Aeronautics and Space Administration (NASA) Graduate Student Research Program NGT-2–52230 (R. M. Ortiz), and NASA Grants 121–10–50 and 121–40–10 (C. E. Wade). This research was conducted in partial fulfillment of the requirements for the doctorate degree in biology for R. M. Ortiz. Research was conducted under National Marine Fisheries Service marine mammal permit #836 to C. L. Ortiz and UCSC Chancellor's Animal Research Committee permit Orti89.08 to C. L. Ortiz and R. M. Ortiz. Address for reprint requests and other correspondence: R. M. Ortiz (E-mail: rortiz@mail.arc.nasa.gov ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2001 the American Physiological Society

Journal

AJP - Regulatory, Integrative and Comparative PhysiologyThe American Physiological Society

Published: Mar 1, 2001

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create folders to
organize your research

Export folders, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off