Turtles maintain mitochondrial integrity but reduce mitochondrial respiratory capacity in the heart after cold acclimation and anoxia

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Amanda Bundgaard, Klaus Qvortrup, Lene Juel Rasmussen, Angela Fago

Mitochondria are important to cellular homeostasis, but can become a dangerous liability when cells recover from hypoxia. Anoxia-tolerant freshwater turtles show reduced mitochondrial respiratory capacity and production of reactive oxygen species (ROS) after prolonged anoxia, but the mechanisms are unclear. Here, we investigated whether this mitochondrial suppression originates from downregulation of mitochondrial content or intrinsic activity by comparing heart mitochondria from (1) warm (25 degrees C) normoxic, (2) cold-acclimated (4 degrees C) normoxic and (3) cold-acclimated anoxic turtles. Transmission electron microscopy of heart ventricle revealed that these treatments did not affect mitochondrial volume density and morphology. Furthermore, neither enzyme activity, protein content nor supercomplex distribution of electron transport chain (ETC) enzymes changed significantly. Instead, our data imply that turtles inhibit mitochondrial respiration rate and ROS production by a cumulative effect of slight inhibition of ETC complexes. Together, these results show that maintaining mitochondrial integrity while inhibiting overall enzyme activities are important aspects of anoxia tolerance.
Original languageEnglish
Article numberjeb200410
JournalJournal of Experimental Biology
Volume222
Issue number11
Number of pages9
ISSN0022-0949
DOIs
Publication statusPublished - 2019

    Research areas

  • Electron microscopy, Respirometry, Mitochondria, Reactive oxygen species, Supercomplex, Oxygen

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