title: Endurance training-induced changes in alkali light chain patterns in type IIB fibers of the rat.
abstract: The effects of endurance training on the expression of myosin were electrophoretically analyzed in the deep portion of vastus lateralis muscle from the rat. A 10-wk running program led to increases (P < 0.01) in myosin heavy chain (MHC) 2a and 2d with a decrease (P < 0.01) in MHC(2b). Training also evoked a rearrangement of the isomyosin pattern with decreases in fast isomyosin (FM) 1 (P < 0.01) and FM2 (P < 0.05) and a rise in intermediate isomyosin (P < 0.01). These changes were accompanied by a 61% decrease (P < 0.01) in myosin light chain (MLC) 3F (11.8 +/- 2.7 vs. 4.6 +/- 4.2%). Two-dimensional electrophoresis made it possible to separate the triplet of isomyosins (FMb) consisting of MHC(2b). Training elicited a 26% decrease (P < 0.05) in the FM1b fraction within FMb, i.e., FM1b/(FM1b + FM2b + FM3b) (24.2 +/- 5.5 vs. 18.0 +/- 4.3%). These changes resulted in a 10% decrease (P < 0.05) in the MLC(3F) fraction, i.e., MLC(3F)/(MLC(1F) + MLC(3F)), in FMb (44.9 +/- 4.5 vs. 40.3 +/- 3.2%). These results suggest that endurance training may exert the depressive effect on the contractile velocity of type IIB fibers and that a training-induced decrease in the contractile velocity of whole muscle may be caused by alterations in fast alkali MLC complements within a given fiber type as well as by transitions in MHC-based fiber populations.
authors.affiliation: Faculty of Integrated Arts and Sciences, Faculty of Medicine, Hiroshima University, Higashihiroshima, Japan. wada@hiroshima-u.ac.jp
authors.forename: Masanobu
authors.initials: M
authors.lastname: Wada
authors.forename: Shuichiro
authors.initials: S
authors.lastname: Inashima
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamada
authors.forename: Satoshi
authors.initials: S
authors.lastname: Matsunaga
mesh_terms: D000468:Alkalies; D000818:Animals; D003720:Densitometry; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D007536:Isomerism; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000378:metabolism; D018994:Myosin Light Chains / Q000737:chemistry / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000468:Alkalies; D018994:Myosin Light Chains; D018995:Myosin Heavy Chains