Gnaiger 2011 Abstract-MonteVerita
|Gnaiger E (2011) Mitochondrial respiratory capacity at maximum aerobic exercise levels: Are intracellular oxygen levels limiting? Abstract Monte Verita.|
Gnaiger E (2011)
Event: Monte Verita
Mitochondrial capacity: OXPHOS capacity is evaluated in isolated mitochondria (mt) and permeabilized cells with physiological substrate cocktails to reconstitute tricarboxylic acid cycle function. As a consequence, convergent electron flow from Complexes CI+II of the electron transfer system (ETS) to the Q-junction exerts an additive effect on flux .
Oxygen kinetics of mt-respiration: The apparent Km,O2 or c50 [µM] (p50 [kPa]) of mt-respiration increases linearly with respiratory capacity controlled by metabolic state, from 0.2 to 1.6 µM determined by high-resolution respirometry. O2 gradients are significant only in large cells including cardiomyocytes. The apparent p50 increases 100-fold in permeabilized muscle fibers due to diffusion gradients .
mt-function at VO2max: Aerobic capacity of the human leg muscle exceeds maximum O2 uptake of isolated mitochondria  and v. lateralis during VO2max . Therefore, oxygen supply limits aerobic performance, proportional to the apparent mt-excess capacity . mt-respiration is more sensitive to average pO2 in heterogenous tissues than under homogenous conditions in vitro. Tissue heterogeneity increases the kinetic dependence of flux on average intracellular pO2. High mt-density reinforces the steepness of oxygen gradients and oxygen heterogeneity in the tissue, contributing to the O2 limitation in athletic vs sedentary individuals at VO2max . This provides a functional rationale for the observation that hypoxia does not specifically trigger mt-biogenesis .
Contribution to K-Regio MitoCom Tyrol.
 Rasmussen et al 2001 AJP.
 Richardson et al; Haseler et al JAP.
• MiPNetLab: AT Innsbruck Gnaiger E
Labels: MiParea: Respiration Mammal;model: Human Regulation: Oxygen kinetics, Substrate Coupling state: OXPHOS Substrate state: CI, CII, CI&II HRR: Oxygraph-2k