Description
Biochemical cell ergometry aims at measurement of JO2max (compare VO2max or VO2peak in exercise ergometry of humans and animals) of cell respiration linked to phosphorylation of ADP to ATP. The corresponding OXPHOS capacity is based on saturating concentrations of ADP, [ADP]*, and inorganic phosphate, [Pi]*, available to the mitochondria. This is metabolically opposite to uncoupling respiration, which yields ET-capacity. The OXPHOS state can be established experimentally by selective permeabilization of cell membranes with maintenance of intact mitochondria, titrations of ADP and Pi to evaluate kinetically saturating conditions, and establishing fuel substrate combinations which reconstitute physiological TCA cycle function. Uncoupler titrations are applied to determine the apparent ET-pathway excess over OXPHOS capacity and to calculate OXPHOS- and ET-pathway coupling efficiency , j≈P and j≈E. These normalized flux ratios are the basis to calculate the ergometric or ergodynamic efficiency, ε = j · f, where f is the normalized force ratio.
Reference: Gnaiger 2014 MitoPathways
MitoPedia concepts:
MiP concept
MitoPedia methods:
Respirometry
Cell ergometry and OXPHOS
Gnaiger E (2015) Cell ergometry and OXPHOS. Mitochondr Physiol Network 2015-01-18. |
Abstract: Spiroergometry on the organismic level is compared to cell ergometry as OXPHOS analysis on the cellular level.
• O2k-Network Lab: AT Innsbruck Gnaiger E
Labels:
Regulation: Coupling efficiency;uncoupling
Coupling state: LEAK, OXPHOS, ET
Pathway: N, S, NS, ROX
HRR: Theory
Figure 1: Coupling control protocol in the intact cell
Spiroergometry
- VO2max or VO2peak in cycle or treadmill spiroergometry is expressed in units of [ml O2·min-1·kg-1] body mass. 1 ml oxygen at STPD is equivalent to 22.392 mmol O2. Therefore, multiply by 1000/(22.392·60)=0.744 to convert VO2peak to JO2peak expressed in SI units [nmol·s-1·g-1]:
1 ml O2·min-1·kg-1 = 0.744 µmol·s-1·kg-1
- VO2peak (JO2peak) typically declines from 70 to 25 ml O2·min-1·kg-1 (50 to 20 µmol·s-1·kg-1) in the range of healthy trained to obese untrained humans.
Cell ergometry: intact cells
Respiratory coupling states in intact cells
- ROUTINE respiration, R = R´-Rox
- Free ROUTINE activity, ≈R = R-L
- ET-capacity, E = E´-Rox
- Free ET-capacity, ≈E = E-L
- Excess E-R capacity, ExR = E-R
- LEAK respiration, L = L´-Rox
- Residual oxygen consumption, ROX (subtracted from apparent fluxes (R´, E´, L´)
- ROUTINE respiration, R = R´-Rox
Respiratory coupling control ratios in intact cells
- L/R coupling control ratio, L/R
- LEAK control ratio, L/E
- ROUTINE control ratio, R/E
Respiratory coupling control factors in intact cells
- ROUTINE coupling efficiency: j≈R = ≈R/R =(R-L)/R = 1-L/R
- ET-pathway coupling efficiency, E-L control factor: j≈E = ≈E/E = (E-L)/E = 1-L/E
- Excess E-R capacity factor, E-R coupling control factor: jExR = (E-R)/E = 1-R/E
- netROUTINE control ratio, ≈R/E control ratio: ≈R/E = (R-L)/E
Cell ergometry: permeabilized cells
Respiratory coupling states in mt-preparations
- OXPHOS capacity, P = P´-Rox
- Free OXPHOS capacity, ≈P = P-L
- ET-capacity, E = E´-Rox
- Free ET-capacity, ≈E = E-L
- Excess E-P capacity, ExP = E-P
- LEAK respiration, L = L´-Rox
- Residual oxygen consumption, Rox (subtracted from P´, E´, L´)
- OXPHOS capacity, P = P´-Rox
Respiratory coupling control ratios in mt-preparations
- L/P coupling control ratio: L/P
- LEAK control ratio, L/E
- OXPHOS control ratio, P/E
Respiratory coupling control factors in mt-preparations
- OXPHOS coupling efficiency, (P-L or ≈P control factor): j≈P = ≈P/P = (P-L)/P = 1-L/P
- ET-pathway coupling efficiency, E-L control factor: j≈E = ≈E/E = (E-L)/E = 1-L/E
- Excess E-P capacity factor, E-P coupling control factor: jExP = (E-P)/E = 1-P/E
- netOXPHOS control ratio, ≈P/E control ratio: ≈P/E = (P-L)/E