Meszaros 2018 EBEC2018

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Tissue- and substrate-specific patterns in the oxygen kinetics of mitochondrial respiration.

Link: EBEC2018

Meszaros AT, Haider M, Gnaiger E (2018)

Event: EBEC2018

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 [1] and that mt p50 (pO2 at half-maximum O2 flux, JO2) is a function of coupling and JO2 [2]. 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.


Bioblast editor: Kandolf G, Meszaros AT O2k-Network Lab: AT Innsbruck Gnaiger E, AT Innsbruck Oroboros


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:HRR: Oxygraph-2k  Event: Oral 


Affiliations

Mészáros A(1,2), Haider M(3), Gnaiger E(1,4)

  1. Oroboros Instruments, Innsbruck, Austria
  2. Inst Surgical Research, Univ Szeged, Hungary
  3. Steinhauser & Haider Technology Consulting OG, Innsbruck, Austria
  4. D. Swarovski Research Lab, Dept Visceral, Transplant Thoracic Surgery, Medical Univ Innsbruck, Austria. - andras.meszaros@oroboros.at

References

  1. Krab K, Kempe H, Wikström M (2011) Explaining the enigmatic KM for oxygen in cytochrome c oxidase: A kinetic model. BBA 1807:348–58
  2. 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.