Cardiac mitochondrial function, nitric oxide sensitivity and lipid composition following hypoxia acclimation in...

Area of Science:

• Cardiovascular physiology
• Mitochondrial function
• Hypoxia adaptation

Background:

• Cardiac mitochondrial function under oxygen limitation is poorly understood in fish.
• Sablefish experience variable oxygen levels, making them a relevant model for hypoxia studies.

Purpose of the Study:

• To investigate the effects of chronic hypoxia acclimation and acute anoxia-reoxygenation on sablefish cardiac mitochondrial respiration and reactive oxygen species (ROS) release.
• To examine how hypoxia affects mitochondrial sensitivity to nitric oxide (NO) and alters mitochondrial lipid and fatty acid composition.

Main Methods:

• High-resolution fluorespirometry was used to measure mitochondrial respiration and ROS production.
• Sablefish underwent in vivo hypoxia acclimation followed by in vitro anoxia-reoxygenation protocols.
• Mitochondrial fatty acid composition and sensitivity to NO inhibition were analyzed.

Main Results:

• Hypoxia acclimation did not affect basal mitochondrial respiration or ROS release rates.
• Acclimation increased citrate synthase activity and enhanced post-anoxia respiratory recovery and reduced ROS release.
• Mitochondrial respiration became more sensitive to NO inhibition, and fatty acid composition shifted, notably increasing arachidonic and eicosapentaenoic acids.

Conclusions:

• Hypoxia acclimation may protect sablefish cardiac bioenergetic function during oxygen limitation.
• Adaptations in mitochondrial NO sensitivity and membrane composition (fluidity) likely contribute to this protection.