Galli 2013 J Exp Biol

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Galli GL, Lau GY, Richards JG (2013) Beating oxygen: chronic anoxia exposure reduces mitochondrial F1FO-ATPase activity in turtle (Trachemys scripta) heart. J Exp Biol 216:3283-93.

» PMID: 23926310 Open Access

Galli GL, Lau GY, Richards JG (2013) J Exp Biol

Abstract: The freshwater turtle Trachemys scripta can survive in the complete absence of O2 (anoxia) for periods lasting several months. In mammals, anoxia leads to mitochondrial dysfunction, which culminates in cellular necrosis and apoptosis. Despite the obvious clinical benefits of understanding anoxia tolerance, little is known about the effects of chronic oxygen deprivation on the function of turtle mitochondria. In this study, we compared mitochondrial function in hearts of T. scripta exposed to either normoxia or 2 weeks of complete anoxia at 5°C and during simulated acute anoxia/reoxygenation. Mitochondrial respiration, electron transport chain activities, enzyme activities, proton conductance and membrane potential were measured in permeabilised cardiac fibres and isolated mitochondria. Two weeks of anoxia exposure at 5°C resulted in an increase in lactate, and decreases in ATP, glycogen, pH and phosphocreatine in the heart. Mitochondrial proton conductance and membrane potential were similar between experimental groups, while aerobic capacity was dramatically reduced. The reduced aerobic capacity was the result of a severe downregulation of the F1FO-ATPase (Complex V), which we assessed as a decrease in enzyme activity. Furthermore, in stark contrast to mammalian paradigms, isolated turtle heart mitochondria endured 20 min of anoxia followed by reoxygenation without any impact on subsequent ADP-stimulated O2 consumption (State III respiration) or State IV respiration. Results from this study demonstrate that turtle mitochondria remodel in response to chronic anoxia exposure and a reduction in Complex V activity is a fundamental component of mitochondrial and cellular anoxia survival.

Keywords: Anoxia, Electron transport chain, Heart, Hypoxia, Mitochondria, Oxidative phosphorylation, Proton conductance, Turtle

O2k-Network Lab: UK Manchester Galli GL, CA Vancouver Richards JG

Labels: MiParea: Respiration, Comparative MiP;environmental MiP, mt-Awareness 

Stress:Ischemia-reperfusion  Organism: Reptiles  Tissue;cell: Heart  Preparation: Permeabilized tissue, Isolated mitochondria 

Coupling state: LEAK, OXPHOS  Pathway: N, S, CIV  HRR: Oxygraph-2k, TPP