Meszaros 2018 EBEC2018
|Tissue- and substrate-specific patterns in the oxygen kinetics of mitochondrial respiration.|
In most tissues mitochondria (mt) respire in a low oxygen (O2) environment, where intracellular partial O2 pressures (pO2) may exert control over OXPHOS. It is well established that the affinity of cytochrome c oxidase (CIV) for O2 decreases with increasing enzyme turnover  and that mt p50 (pO2 at half-maximum O2 flux, JO2) is a function of coupling and JO2 . In our study of tissue-specific O2 kinetics, we investigated the influence of pathway and coupling control on mt p50 with various fuel substrates in OXPHOS-, LEAK- and ET-states in mt isolated from mouse brain, heart and liver.
Isolated mt were incubated in Oroboros O2k High-Resolution FluoRespirometers. Kinetic data was obtained during aerobic-anaerobic transitions with high time-resolution. p50 values were calculated using the O2kinetics software for automatic calibration and correction of O2 signals, data processing and curve fitting.
p50 ranged from 0.006 to 0.07 kPa for NADH-linked LEAK respiration with glutamate&malate (GM), and NADH-&succinate-linked OXPHOS capacity with GM and pyruvate, in agreement with and extending the literature. p50 increased with an increase from 25 °C to 37 °C. In heart and liver, p50 was higher in OXPHOS- than in LEAK-states, increasing proportionally with CIV turnover. Surprisingly, however, brain mt did not follow this kinetic pattern in S-linked coupling control states, irrespective of rotenone addition, with p50 values in LEAK up to 2-times higher than in OXPHOS, despite a 3-4 fold decline of JO2. Further studies are underway to elucidate the underlying mechanisms, and to address the question if mouse brain is an exception or representative of a general pattern.
Labels: MiParea: Respiration
Organism: Mouse Tissue;cell: Heart, Nervous system, Liver Preparation: Isolated mitochondria Enzyme: Complex IV;cytochrome c oxidase Regulation: Oxygen kinetics Coupling state: LEAK, OXPHOS, ET Pathway: N HRR: Oxygraph-2k Event: Oral
Mészáros A(1,2), Haider M(3), Gnaiger E(1,4)
- Oroboros Instruments, Innsbruck, Austria
- Inst Surgical Research, Univ Szeged, Hungary
- Steinhauser & Haider Technology Consulting OG, Innsbruck, Austria
- D. Swarovski Research Lab, Dept Visceral, Transplant Thoracic Surgery, Medical Univ Innsbruck, Austria. - [email protected]
- Krab K, Kempe H, Wikström M (2011) Explaining the enigmatic KM for oxygen in cytochrome c oxidase: A kinetic model. BBA 1807:348–58
- Gnaiger E, Steinlechner-Maran R, Méndez G, Eberl T, Margreiter R (1995) Control of mitochondrial and cellular respiration by oxygen. J Bioenerg Biomembr 27:583-96.