Cell ergometry

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Cell ergometry

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 ETS 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 ETS excess over OXPHOS capacity and to calculate OXPHOS- and ETS coupling efficiencies, 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.

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Reference: Gnaiger 2014 MitoPathways


MitoPedia concepts: MiP concept 


MitoPedia methods: Respirometry 

Cell ergometry and OXPHOS

Publications in the MiPMap
Gnaiger E (2015) Cell ergometry and OXPHOS. Mitochondr Physiol Network 2015-01-18.

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OROBOROS (2015) MiPNet

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, ETS  Pathway: N, S, NS, ROX  HRR: Theory 



Cell ergometry.jpg


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 ROUTINE respiration, R = -ROX
Free ROUTINE activity Free ROUTINE activity, ≈R = R-L
ETS ETS capacity, E = -ROX
Free ETS capacity Free ETS capacity, ≈E = E-L
Excess E-R capacity Excess E-R capacity, ExR = E-R
LEAK LEAK respiration, L = -ROX
ROX Residual oxygen consumption, ROX (subtracted from apparent fluxes (R´, E´, L´)


Respiratory coupling control ratios in intact cells

L/R coupling control ratio L/R coupling control ratio, L/R
LEAK control ratio LEAK control ratio, L/E
ROUTINE control ratio ROUTINE control ratio, R/E


Respiratory coupling control factors in intact cells

ROUTINE coupling efficiency ROUTINE coupling efficiency: j≈R = ≈R/R =(R-L)/R = 1-L/R
ETS coupling efficiency ETS coupling efficiency, E-L control factor: j≈E = ≈E/E = (E-L)/E = 1-L/E
Excess E-R capacity factor Excess E-R capacity factor, E-R coupling control factor: jExR = (E-R)/E = 1-R/E
netROUTINE control ratio netROUTINE control ratio, ≈R/E control ratio: ≈R/E = (R-L)/E


Cell ergometry: permeabilized cells

Respiratory coupling states in mt-preparations

OXPHOS OXPHOS capacity, P = -ROX
Free OXPHOS capacity Free OXPHOS capacity, ≈P = P-L
ETS ETS capacity, E = -ROX
Free ETS capacity Free ETS capacity, ≈E = E-L
Excess E-P capacity Excess E-P capacity, ExP = E-P
LEAK LEAK respiration, L = -ROX
ROX Residual oxygen consumption, ROX (subtracted from P´, E´, L´)


Respiratory coupling control ratios in mt-preparations

L/P coupling control ratio L/P coupling control ratio: L/P
LEAK control ratio LEAK control ratio, L/E
OXPHOS control ratio OXPHOS control ratio, P/E


Respiratory coupling control factors in mt-preparations

OXPHOS coupling efficiency OXPHOS coupling efficiency, (P-L or ≈P control factor): j≈P = ≈P/P = (P-L)/P = 1-L/P
ETS coupling efficiency ETS coupling efficiency, E-L control factor: j≈E = ≈E/E = (E-L)/E = 1-L/E
Excess E-P capacity factor Excess E-P capacity factor, E-P coupling control factor: jExP = (E-P)/E = 1-P/E
netOXPHOS control ratio netOXPHOS control ratio, ≈P/E control ratio: ≈P/E = (P-L)/E