Anoxia-induced changes in reactive oxygen species and cyclic nucleotides in the painted turtle |
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Authors: | Matthew Edward Pamenter Michael David Richards Leslie Thomas Buck |
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Institution: | (1) Department of Cell and Systems Biology, and Department of Ecology and Evolutionary Biology, University of Toronto, 25 Harbord St., Toronto, ON, Canada, M5S 3G5 |
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Abstract: | The Western painted turtle survives months without oxygen. A key adaptation is a coordinated reduction of cellular ATP production
and utilization that may be signaled by changes in the concentrations of reactive oxygen species (ROS) and cyclic nucleotides
(cAMP and cGMP). Little is known about the involvement of cyclic nucleotides in the turtle’s metabolic arrest and ROS have
not been previously measured in any facultative anaerobes. The present study was designed to measure changes in these second
messengers in the anoxic turtle. ROS were measured in isolated turtle brain sheets during a 40-min normoxic to anoxic transition.
Changes in cAMP and cGMP were determined in turtle brain, pectoralis muscle, heart and liver throughout 4 h of forced submergence
at 20–22°C. Turtle brain ROS production decreased 25% within 10 min of cyanide or N2-induced anoxia and returned to control levels upon reoxygenation. Inhibition of electron transfer from ubiquinol to complex
III caused a smaller decrease in ROS]. Conversely, inhibition of complex I increased ROS] 15% above controls. In brain cAMP]
decreased 63%. In liver cAMP] doubled after 2 h of anoxia before returning to control levels with prolonged anoxia. Conversely,
skeletal muscle and heart cAMP] remained unchanged; however, skeletal muscle cGMP] became elevated sixfold after 4 h of
submergence. In liver and heart cGMP] rose 41 and 127%, respectively, after 2 h of anoxia. Brain cGMP] did not change significantly
during 4 h of submergence. We conclude that turtle brain ROS production occurs primarily between mitochondrial complexes I
and III and decreases during anoxia. Also, cyclic nucleotide concentrations change in a manner suggestive of a role in metabolic
suppression in the brain and a role in increasing liver glycogenolysis. |
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Keywords: | Turtle Anoxia Reactive oxygen species Cyclic-AMP Cyclic-GMP |
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