Oxygen Transport to Tissue XXXI pp 7-25
Cell Respiration Under Hypoxia: Facts and Artefacts in Mitochondrial Oxygen Kinetics
- Cite this paper as:
- Scandurra F.M., Gnaiger E. (2010) Cell Respiration Under Hypoxia: Facts and Artefacts in Mitochondrial Oxygen Kinetics. In: Takahashi E., Bruley D. (eds) Oxygen Transport to Tissue XXXI. Advances in Experimental Medicine and Biology, vol 662. Springer, Boston, MA
When oxygen supply to tissues is limiting, mitochondrial respiration and ATP production are compromised. To assess the bioenergetic consequences under normoxia and hypoxia, quantitative evaluation of mitochondrial oxygen kinetics is required. Using high-resolution respirometry, the “apparent Km” for oxygen or p50 of respiration in 32D cells was determined at 0.05 ± 0.01 kPa (0.4 mmHg, 0.5 μM, 0.25% air saturation). Close agreement with p50 of isolated mitochondria indicates that intracellular gradients are small in small cells at routine activity. At intracellular pO2 <2 kPa (15 mmHg, 10% air saturation) in various tissues under normoxia, respiration is limited by >2% with a p50 of 0.05 kPa. Over-estimation of p50 at 0.4 kPa (3 mmHg) would imply significant (>17%) oxygen limitation of respiration under intracellular normoxia. Based on a critical review, we conclude that p50 ranges from 0.01 to 0.10 kPa in mitochondria and small cells in the absence of inhibitors of cytochrome c oxidase, whereas experimental artefacts explain the controversial >200-fold range of p50 in the literature on mitochondrial oxygen kinetics.