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Non-weight bearing-induced muscle weakness: the role of myosin quantity and quality in MHC type II fibers

Title
Non-weight bearing-induced muscle weakness: the role of myosin quantity and quality in MHC type II fibers
Author
김종희
Keywords
disuse; specific tension; inactivity; exercise; non-weight bearing
Issue Date
2014-07
Publisher
American Physical Society
Citation
American Journal of Physiology, 2014, 307(2), P.190-194
Abstract
We tested the hypothesis that non-weight bearing-induced muscle weakness (i.e., specific force) results from decreases in myosin protein quantity (i.e., myosin content per half-sarcomere and the ratio of myosin to actin) and quality (i.e., force per half-sarcomere and population of myosin heads in the strong-binding state during muscle contraction) in single myosin heavy chain (MHC) type II fibers. Fisher-344 rats were assigned to weight-bearing control (Con) or non-weight bearing (NWB). The NWB rats were hindlimb unloaded for 2 wk. Diameter, force, and MHC content were determined in permeabilized single fibers from the semimembranosus muscle. MHC isoform and the ratio of MHC to actin in each fiber were determined by gel electrophoresis and silver staining techniques. The structural distribution of myosin from spin-labeled fiber bundles during maximal isometric contraction was evaluated using electron paramagnetic resonance spectroscopy. Specific force (peak force per cross-sectional area) in MHC type IIB and IIXB fibers from NWB was significantly reduced by 38% and 18%, respectively. MHC content per half-sarcomere was significantly reduced by 21%. Two weeks of hindlimb unloading resulted in a reduced force per half-sarcomere of 52% and fraction of myosin strong-binding during contraction of 34%. The results suggest that reduced myosin and actin content (quantity) and myosin quality concomitantly contribute to non-weight bearing-related muscle weakness.
URI
https://www.physiology.org/doi/10.1152/ajpcell.00076.2014http://hdl.handle.net/20.500.11754/53479
ISSN
0363-6143; 1522-1563
DOI
10.1152/ajpcell.00076.2014
Appears in Collections:
COLLEGE OF ART AND PHYSICAL EDUCATION[S](예술·체육대학) > ETC
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