Cell ergometry

high-resolution terminology - matching measurements at high-resolution

Cell ergometry

Description

Biochemical cell ergometry aims at measurement of J_O2max (compare V_O2max or V_O2peak 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 P_i 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.

Abbreviation: n.a.

Reference: Gnaiger 2014 MitoPathways

MitoPedia methods: Respirometry 

MitoPedia topics: "Respiratory state" is not in the list (Enzyme, Medium, Inhibitor, Substrate and metabolite, Uncoupler, Sample preparation, Permeabilization agent, EAGLE, MitoGlobal Organizations, MitoGlobal Centres, ...) of allowed values for the "MitoPedia topic" property. Respiratory state"Respiratory state" is not in the list (Enzyme, Medium, Inhibitor, Substrate and metabolite, Uncoupler, Sample preparation, Permeabilization agent, EAGLE, MitoGlobal Organizations, MitoGlobal Centres, ...) of allowed values for the "MitoPedia topic" property. 

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Spiroergometry

V_O2max or V_O2peak 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 V_O2peak to J_O2peak expressed in SI units [nmol·s^-1·g^-1]:

1 ml O2·min-1·kg-1 = 0.744 µmol·s-1·kg-1

V_O2peak (J_O2peak) 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

ETS capacity, E

LEAK respiration, L

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

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

ETS 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: j_ExR = (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

ETS capacity, E

LEAK respiration, L

Residual oxygen consumption, ROX (subtracted from apparent fluxes (R´, E´, L´)

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

ETS 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: j_ExP = (E-P)/E = 1-P/E

netOXPHOS control ratio, ≈P/E control ratio: ≈P/E = (P-L)/E