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Diaphragm and limb muscles adapt differently to chronic normobaric hypoxia in mice
Author(s) -
Gamboa Jorge Luis,
Andrade Francisco H.
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1110.8
Subject(s) - hypoxia (environmental) , medicine , respiration , endocrinology , skeletal muscle , mitochondrion , biology , respiratory system , anatomy , chemistry , oxygen , biochemistry , organic chemistry
The adaptation of skeletal muscle to high altitude includes loss of oxidative capacity and smaller fiber size. Past studies focused on limb muscles, less active while animals adapt to lower Po2. In contrast, the diaphragm (DIA) increases its activity during hypoxia and may retain its endurance. We hypothesized that chronic hypoxia would not affect endurance, mitochondrial function or fiber size in the mouse DIA. Adult male mice were kept in normoxia (Control) or normobaric hypoxia (Hypoxia, FIO2= 10%) for 4 weeks. We measured endurance in vitro, mean fiber area (MFA), and mitochondrial function in DIA and leg muscles. The Hypoxia leg muscles had less endurance, but there was no difference between Control and Hypoxia DIA. MFA was unchanged in the Hypoxia leg muscles and 25% smaller in DIA (p<0.001). Mitochondrial respiration rates in Hypoxia leg muscles were slower: state 2 decreased 19%, state 3, 31% and state 4, 18%, p<0.05 for all comparisons. There were similar changes in the Hypoxia DIA: state 3 decreased 29% and state 4, 17%, p<0.05. However, Hypoxia altered mitochondrial composition differently in the two muscles: leg muscle mitochondria had less respiratory complex IV, while DIA mitochondria had more respiratory complexes IV and V and less UCP3. These data demonstrate that DIA retains its endurance during chronic hypoxia, probably due to shorter diffusion distances and optimized mitochondrial energy production.