QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online May 30, 2008
Journal of Experimental Biology 211, 1911-1918 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.016519

This Article Figures Only Full Text Full Text (PDF) Supplementary Material Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JEB Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by Trzcionka, M. Articles by Jastroch, M. PubMed PubMed Citation Articles by Trzcionka, M. Articles by Jastroch, M.

The effects of fasting and cold exposure on metabolic rate and mitochondrial proton leak in liver and skeletal muscle of an amphibian, the cane toad Bufo marinus

M. Trzcionka^1,*, K. W. Withers², M. Klingenspor¹ and M. Jastroch¹

¹ Department of Animal Physiology, Faculty of Biology, Philipps-Universität Marburg, Karl-von-Frisch-Strasse 8, 35043 Marburg, Germany
² Centre for Systems Biology, University of Southern Queensland, Toowoomba, Queensland, Australia

^* Author for correspondence (e-mail: trzcionk{at}students.uni-marburg.de)

Accepted 7 April 2008

Futile cycling of protons across the mitochondrial inner membrane contributes significantly to standard metabolic rate in a variety of ectothermic and endothermic animals, but adaptations of the mitochondrial bioenergetics to different environmental conditions have rarely been studied in ectotherms. Changes in ambient temperature and nutritional status have a great effect on the physiological demands of ectothermic amphibians and may require the adjustment of mitochondrial efficiency. In order to investigate the effect of temperature and nutritional status on the mitochondrial level, we exposed male cane toads to either 10°C or 30°C and fasted half of the animals in each group. Cold exposure resulted in a fourfold reduction of the resting metabolic rate whereas nutritional status had only minor effects. The mitochondrial adjustments to each condition were observed by comparing the proton leak kinetics of isolated liver and skeletal muscle mitochondria at 25°C. In response to cold exposure, liver mitochondria showed a decrease in proton conductance while skeletal muscle mitochondria were unchanged. Additional food deprivation had minor effects in skeletal muscle, but in liver we uncovered surprising differences in energy saving mechanisms between the acclimation temperatures: in warm-acclimated toads, fasting resulted in a decrease of the proton conductance whereas in cold-acclimated toads, the activity of the respiratory chain was reduced. To investigate the molecular mechanism underlying mitochondrial proton leakage, we determined the adenine-nucleotide transporter (ANT) content, which explained tissue-specific differences in the basal proton leak, but neither the ANT nor uncoupling protein (UCP) gene expression correlated with alterations of the proton leak in response to physiological stimuli.

Key words: mitochondrial respiration, adenine nucleotide translocase (ANT), uncoupling protein (UCP), Xenopus laevis, carboxyatractylate (CAT)

Related articles in JEB:

COLD CANE TOADS CUT PROTON LEAK

Kathryn Phillips
JEB 2008 211: ii. [Full Text]  

This article has been cited by other articles:

				K. Phillips COLD CANE TOADS CUT PROTON LEAK J. Exp. Biol., June 15, 2008; 211(12): ii - ii. [Full Text] [PDF]