title: The effects of eccentric contraction on myofibrillar proteins in rat skeletal muscle.
abstract: The present study investigated the effects of eccentric muscle contractions (ECC) on the content of myofibrillar proteins (my-proteins) and the catalytic activity of myofibrillar ATPase (my-ATPase) in skeletal muscles. Rat extensor digitorum longus and tibialis anterior muscles were exposed to 200-repeated ECC or isometric contractions (ISC) and used for measures of force output and for biochemical analyses, respectively. Whereas in ISC-treated muscles, full restoration of tetanic force was attained after 2 days of recovery, force developed by ECC-treated muscles remained depressed (P < 0.05) after 6 days. The total my-protein content and the relative content of myosin heavy chain (MHC) in total my-proteins were unaltered during 4 days of recovery after ECC, but fell (P < 0.05) to 55.9 and 63.4% after 6 days of recovery, respectively. my-ATPase activity expressed on a my-protein weight basis was unaltered immediately after ECC. However, it decreased (P < 0.05) to 75.3, 45.3, and 49.3% after 2, 4 and 6 days of recovery, respectively. Total maximal calpain activity measured at 5 mM Ca(2+) was significantly augmented (P < 0.05) after 2 days of recovery, reaching a level of threefold higher after 6 days. These alterations were specific for ECC and not observed for ISC. These results suggest that depressions in my-ATPase activity contribute to ECC-induced decreases in force and power which can take a number of days to recover.
authors.affiliation: Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima, Hiroshima, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Kanzaki
authors.forename: Mai
authors.initials: M
authors.lastname: Kuratani
authors.forename: Takaaki
authors.initials: T
authors.lastname: Mishima
authors.forename: Satoshi
authors.initials: S
authors.lastname: Matsunaga
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Yanaka
authors.forename: Sachio
authors.initials: S
authors.lastname: Usui
authors.forename: Masanobu
authors.initials: M
authors.lastname: Wada
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism / Q000502:physiology; D000818:Animals; D002154:Calpain / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D035002:Lower Extremity / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009124:Muscle Proteins / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D009210:Myofibrils / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000032:analysis / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D009124:Muscle Proteins; D002154:Calpain; D000251:Adenosine Triphosphatases; D018995:Myosin Heavy Chains