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Skeletal muscle oxidative function after a 10-day exposure to hypoxia and microgravity
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.ORCID iD: 0000-0002-7440-2171
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2013 (English)Conference paper, Abstract (Refereed)
Abstract [en]

Skeletal muscle oxidative function was evaluated before (CTRL) and after 10 days of normobaric hypoxic (inspired PO2 12.5kPa) bed rest (H-BR) and normoxic bed rest (BR) in nine healthy young men (age: 24.1±1.7 years [mean±SD]). H-BR was taken as a simulation of lunar habitats. Pulmonary gas exchange and vastus lateralis muscle fractional O2-extraction (by near-infrared spectroscopy) were determined during an incremental cycle ergometer (CE) and one-leg knee extension (KE) exercise up to volitional exhaustion. Mitochondrial respiration was evaluated by high-resolution respirometry in permeabilized vastus lateralis fibers. During CE, peak pulmonary O2-uptake ( VO 2peak) significantly decreased by ~7 and 9 % after BR and

H-BR, respectively. During KE, V O 2peak decreased significantly (by ~6%) after BR (0.83±0.07 vs. 0.89±0.08 [CTRL] L·min-1), but not after H-BR (0.86±0.07 vs. 0.90±0.07). Skeletal muscle peak fractional O2-extraction was significantly lower after BR (60±12 vs. 70±11% [CTRL]), but not after H-BR (65±12 vs. 71±10). No significant changes were observed in maximal ADP-stimulated mitochondrial respiration either after BR (48.9±11.5pmolO2·s-1·mg-1 wet weight) or H-BR (42.8±7.8) vs. CTRL (46.6±6.6). After relieving, by the KE exercise protocol, constraints related to cardiovascular O2-delivery, oxidative function in vivo was still impaired after BR, while a less pronounced impairment was evident after H-BR. Mitochondrial respiratory function ex-vivo was unchanged after both conditions. Peripheral O2-diffusion constraints and/or an impaired O2-delivery/O2-utilization coupling might be the main bottleneck to oxidative function in vivo after BR. Hypoxia may attenuate the impairment of muscle oxidative function observed after BR. 

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URN: urn:nbn:se:kth:diva-134619OAI: diva2:667284
EMC 2013 42nd EUROPEAN MUSCLE CONFERENCE; Amsterdam, Netherlands, September 21-25, 2013

QC 20140625

Available from: 2013-11-26 Created: 2013-11-26 Last updated: 2014-06-25Bibliographically approved

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Keramidas, Michail E.Eiken, Ola
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Environmental Physiology

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