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Oxygen diffusion and mitochondrial respiration in neuroblastoma cells
M Robiolio1, W L Rumsey, D F Wilson
1Department of Biochemistry and Biophysics, University of Pennsylvania Medical School, Philadelphia 19104.
The American Journal of Physiology
|June 1, 1989
Summary
Human neuroblastoma cells show oxygen consumption dependent on oxygen pressure below 11 Torr, with a half-maximal respiration pressure (P50) of 0.8 Torr. Uncoupling mitochondria lowers P50, indicating oxygen diffusion limits respiration in these cells.
Area of Science:
- Cellular respiration
- Mitochondrial function
- Neuroblastoma metabolism
Background:
- Human neuroblastoma cells exhibit oxygen consumption patterns influenced by ambient oxygen levels.
- Mitochondrial respiration is crucial for cellular energy production and is sensitive to oxygen availability.
- Previous studies established a P50 value for isolated mitochondria.
Purpose of the Study:
- To investigate the oxygen pressure dependence of respiration in human neuroblastoma cells.
- To determine the effect of altered cellular metabolic states on oxygen consumption and P50.
- To elucidate the role of oxygen diffusion in limiting mitochondrial respiration under various conditions.
Main Methods:
- Measuring oxygen consumption rates of neuroblastoma cell suspensions at varying oxygen pressures.
- Utilizing uncouplers of mitochondrial oxidative phosphorylation to alter cellular energy states.
- Employing amobarbital, a respiratory chain inhibitor, to modulate mitochondrial activity.
- Calculating the oxygen pressure for half-maximal respiration (P50) under different experimental conditions.
Main Results:
- Neuroblastoma cells consumed oxygen at a constant rate above 11 Torr, becoming pressure-dependent below this level.
- The P50 for intact cells was approximately 0.8 Torr, consistent with isolated mitochondria.
- Uncoupling mitochondrial oxidative phosphorylation increased respiration and decreased P50 to ~0.6 Torr.
- In uncoupled cells, P50 further decreased with amobarbital inhibition, suggesting oxygen diffusion limitation.
- For coupled cells, the intracellular-extramitochondrial oxygen gradient was minimal (<0.15 Torr).
Conclusions:
- Oxygen diffusion to mitochondria can limit cellular respiration, particularly in uncoupled neuroblastoma cells.
- The P50 of coupled neuroblastoma cells is primarily determined by intrinsic mitochondrial kinetics, not diffusion gradients.
- Understanding these oxygen dynamics is crucial for interpreting cellular metabolism in hypoxic environments.