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Gnaiger 2001 Respir Physiol

From Bioblast
Publications in the MiPMap
Gnaiger E (2001) Bioenergetics at low oxygen: dependence of respiration and phosphorylation on oxygen and adenosine diphosphate supply. Respir Physiol 128: 277-297.

Β» PMID: 11718759

Gnaiger E (2001) Respir Physiol

Abstract: Oxygen limitation is generally considered as impairment of mitochondrial respiration under hypoxia and ischemia. Low intracellular oxygen levels under normoxia, however, imply mild oxygen limitation, provide protection from oxidative stress, and result from economical strategies for oxygen transport through the respiratory cascade to cytochrome c oxidase. Both perspectives relate to the critical oxygen pressure which inhibits mitochondrial respiration. Based on methodological considerations of oxygen kinetics and a presentation of high-resolution respirometry, mitochondrial oxygen affinities (1/P50) are reviewed with particular emphasis on the turnover effect under control of ADP, which increases the P2 in active states. ADP/O2 flux ratios are high even under severe oxygen limitation, as demonstrated by calorespirometry. Oxygen limitation reduces the uncoupled respiration observed under control by ADP, as shown by relationships derived between ADP/O2 flux ratios, respiratory control ratios, and ADP kinetics. Bioenergetics at low oxygen versus oxidative stress must be considered in the context of limitation of maximum aerobic activity, ischemia-reperfusion injury, mitochondrial signalling to apoptosis, and mitochondrial theories of ageing. β€’ Keywords: Energy: Oxidative phosphorylation, Adenosine diphosphate kinetics, Adenosine diphosphate/O2 ratio; Hypoxia: Mitochondrial O2 kinetics, Mammals: Rat, Membrane permeability, Mitochondria: Heart, Liver

β€’ O2k-Network Lab: AT_Innsbruck_Gnaiger E, AT Innsbruck MitoCom


Labels:

Stress:Hypoxia, RONS; Oxidative Stress"RONS; Oxidative Stress" is not in the list (Cell death, Cryopreservation, Ischemia-reperfusion, Permeability transition, Oxidative stress;RONS, Temperature, Hypoxia, Mitochondrial disease) of allowed values for the "Stress" property.  Organism: Human, Rat  Tissue;cell: Heart, Liver, Endothelial; Epithelial; Mesothelial Cell"Endothelial; Epithelial; Mesothelial Cell" is not in the list (Heart, Skeletal muscle, Nervous system, Liver, Kidney, Lung;gill, Islet cell;pancreas;thymus, Endothelial;epithelial;mesothelial cell, Blood cells, Fat, ...) of allowed values for the "Tissue and cell" property.  Preparation: Intact Cell; Cultured; Primary"Intact Cell; Cultured; Primary" is not in the list (Intact organism, Intact organ, Permeabilized cells, Permeabilized tissue, Homogenate, Isolated mitochondria, SMP, Chloroplasts, Enzyme, Oxidase;biochemical oxidation, ...) of allowed values for the "Preparation" property., Isolated Mitochondria"Isolated Mitochondria" is not in the list (Intact organism, Intact organ, Permeabilized cells, Permeabilized tissue, Homogenate, Isolated mitochondria, SMP, Chloroplasts, Enzyme, Oxidase;biochemical oxidation, ...) of allowed values for the "Preparation" property. 


Coupling state: OXPHOS 

HRR: Oxygraph-2k, TIP2k 

Instrumental and methodological aspects 

Gnaiger 2001 Respir Physiol New Fig10.jpg

Fig. 10 (modified): Opposite effects of ADP limitation and oxygen limitation on mitochondrial membrane potential, and LEAK oxygen flux, JL,O2. The LEAK state is obtained when total oxygen flux equals LEAK respiration. In all other respiratory states, total oxygen flux is the sum of LEAK oxygen flux and mechanistically coupled oxygen flux. A: ADP limitation of respiration at high oxygen levels in the transition from the OXPHOS state (P, saturating ADP) or active State 3 (high ADP) to the resting LEAK state, L (compare State 4), leads to an increase of membrane potential and exponential acceleration of the proton leak (heavy line). Because LEAK oxygen flux increases while total oxygen flux is reduced, the ATP yield (ADP/O2 flux ratio) declines to zero. Turnover-dependent proton leak increases the LEAK oxygen flux in the OXPHOS state but declines towards the LEAK state (Garlid et al 1993). Mitochondrial production of reactive oxygen species (ROS) increases with membrane potential towards the LEAK state, and ROS-linked electron bypass (electron leak) contributes minimally to LEAK oxygen flux at high oxygen (Gnaiger et al 2000). On the right, the decline of ADP/O2 flux ratios is shown in the transition from OXPHOS to LEAK. B: Oxygen limitation of respiration causes a reduction of membrane potential in the transition from ADP limitation at high oxygen, to intracellular conditions of low oxygen and low ADP, to finally severe oxygen limitation under hypoxia and anoxia. Potentially synergistic with the well documented membrane potential effect on LEAK flux, are the hypothetical effects of decreasing membrane permeability and suppression of ROS production under severe hypoxia, whereas intermediary levels of hypoxia may increase ROS production (modified from Gnaiger 2001; see original publication for further references).

* For further discussion, see Oxygen dependence of ROS production - are permeabilized fibres a valid model?.