Premium
Overexpression of antioxidant enzymes in diaphragm muscle does not alter contraction‐induced fatigue or recovery
Author(s) -
McClung Joseph M.,
DeRuisseau Keith C.,
Whidden Melissa A.,
Van Remmen Holly,
Richardson Arlan,
Song Wook,
Vrabas Ioannis S.,
Powers Scott K.
Publication year - 2010
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2009.049650
Subject(s) - diaphragm muscle , contraction (grammar) , diaphragm (acoustics) , muscle contraction , antioxidant , enzyme , muscle fatigue , medicine , chemistry , microbiology and biotechnology , endocrinology , biology , biochemistry , physical medicine and rehabilitation , electromyography , respiratory system , engineering , loudspeaker , electrical engineering
Low levels of reactive oxygen species (ROS) production are necessary to optimize muscle force production in unfatigued muscle. In contrast, sustained high levels of ROS production have been linked to impaired muscle force production and contraction‐induced skeletal muscle fatigue. Using genetically engineered mice, we tested the hypothesis that the independent transgenic overexpression of catalase (CAT), copper/zinc superoxide dismutase (CuZnSOD; SOD1) or manganese superoxide dismutase (MnSOD; SOD2) antioxidant enzymes would negatively affect force production in unfatigued diaphragm muscle but would delay the development of muscle fatigue and enhance force recovery after fatiguing contractions. Diaphragm muscle from wild‐type littermates (WT) and from CAT, SOD1 and SOD2 overexpressing mice were subjected to an in vitro contractile protocol to investigate the force–frequency characteristics, the fatigue properties and the time course of recovery from fatigue. The CAT, SOD1 and SOD2 overexpressors produced less specific force (in N cm −2 ) at stimulation frequencies of 20–300 Hz and produced lower maximal tetanic force than WT littermates. The relative development of muscle fatigue and recovery from fatigue were not influenced by transgenic overexpression of any antioxidant enzyme. Morphologically, the mean cross‐sectional area (in μm 2 ) of diaphragm myofibres expressing myosin heavy chain type IIA was decreased in both CAT and SOD2 transgenic animals, and the percentage of non‐contractile tissue increased in diaphragms from all transgenic mice. In conclusion, our results do not support the hypothesis that overexpression of independent antioxidant enzymes protects diaphragm muscle from contraction‐induced fatigue or improves recovery from fatigue. Moreover, our data are consistent with the concept that a basal level of ROS is important to optimize muscle force production, since transgenic overexpression of major cellular antioxidants is associated with contractile dysfunction. Finally, the transgenic overexpression of independent endogenous antioxidants alters diaphragm skeletal muscle morphology, and these changes may also contribute to the diminished specific force production observed in these animals.