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Updated: Sep 29, 2026
Multi-parameter Measurement of the Permeability Transition Pore Opening in Isolated Mouse Heart Mitochondria
Published on: September 7, 2012
Estimation of the oxygen gradient across phospholipid bilayers of mitochondria from reperfused rabbit hearts after
Abstract:
Mitochondria isolated from myocardium exposed to 30 minute ischemia followed by 30 minute reperfusion showed an increase in membrane viscosity and a decrease in wobbling angle of phospholipids, compared with those from the normally perfused myocardium in anesthetized open-chest rabbits. The values for the membrane viscosity were used to estimate the oxygen gradient across the lipid bilayers of mitochondrial membranes with a model of cylindrical diffusion. The effective diffusion coefficient for oxygen, DO2, was approximated to be 6.5 and 6.3 x 10(-5) cm2/sec in the control and ischemic-reperfused area, respectively, by comparing reported DO2 values with values for membrane viscosity. For the surface area of the inner mitochondrial membrane including cristae and for the oxygen consumption rate of the myocardium, reported values for rats and cats, respectively, were employed. Using these values, oxygen gradients across the lipid bilayers of mitochondrial lipid membranes were estimated to be only 0.055 and 0.057 nM in the control and 30 minute ischemic-reperfused myocardium, respectively. If the mitochondrial membranes are hydrated because of the ischemia-reperfusion, the absorption coefficient of the membrane to oxygen will decrease and the oxygen gradient will be increased. In the present study, however, the fluorescence life time of DPH, the hydrophobic fluorophore, showed no shortening despite the ischemia-reperfusion. Hence, no indication of membrane hydration was obtained.
Insights
Ischemia-reperfusion increases mitochondrial membrane viscosity, impacting oxygen diffusion. However, this study found minimal changes in oxygen gradients across mitochondrial membranes, suggesting no significant hydration occurred.
Area of Science:
- Mitochondrial Physiology
- Cardiovascular Research
- Biophysics
Background:
- Mitochondrial membrane properties change after ischemia-reperfusion.
- Understanding oxygen diffusion across these membranes is crucial for cardiac function.
- Previous studies suggest potential membrane hydration during ischemia-reperfusion.
Purpose of the Study:
- To investigate the impact of ischemia-reperfusion on mitochondrial membrane viscosity and oxygen gradients.
- To determine if ischemia-reperfusion leads to mitochondrial membrane hydration.
- To quantify oxygen diffusion across mitochondrial lipid bilayers post-ischemia.
Main Methods:
- Isolated mitochondria from rabbit myocardium subjected to ischemia-reperfusion.
- Measured mitochondrial membrane viscosity and phospholipid wobbling angle.
- Utilized a cylindrical diffusion model to estimate oxygen diffusion coefficients (DO2).
- Employed literature values for inner mitochondrial membrane surface area and myocardial oxygen consumption rates.
Main Results:
- Ischemia-reperfusion increased mitochondrial membrane viscosity and decreased phospholipid wobbling angle.
- Estimated effective oxygen diffusion coefficients (DO2) were similar in control and ischemic-reperfused groups (6.5 vs. 6.3 x 10(-5) cm2/sec).
- Calculated oxygen gradients across mitochondrial lipid bilayers were minimal (0.055 nM control, 0.057 nM ischemic-reperfused).
- Fluorescence lifetime measurements indicated no significant membrane hydration.
Conclusions:
- Ischemia-reperfusion alters mitochondrial membrane biophysical properties.
- Despite viscosity changes, oxygen gradients across mitochondrial membranes remain largely unaffected.
- The study found no evidence of mitochondrial membrane hydration following ischemia-reperfusion.
