title: Seven skeletal muscles rich in slow muscle fibers may function to sustain neutral position in the rodent hindlimb.
abstract: Skeletal muscles consist of slow-twitch and fast-twitch muscle fibers, which have distinct physiological and biochemical properties. The muscle fiber composition determines the contractile velocity and fatigability of a particular skeletal muscle. We analyzed the systemic distribution of slow muscle fibers in all rodent skeletal muscles by myosin ATPase staining and found that only seven hindlimb skeletal muscles were extremely rich in slow muscle fibers. These included the mouse piriformis (56.5%), gluteus minimus (35.7%), vastus intermedius (24.7%), quadratus femoris (69.9%), adductor brevis (44.3%), gracilis (24.6%), and soleus muscles (35.1%). In mice, the relative proportion of slow muscle fibers did not exceed 15% in skeletal muscles in other regions. The distribution of slow muscle fibers was well conserved in rats and rabbits. The soleus muscle is an important antigravity muscle in both rodents and humans; therefore, these skeletal muscles rich in slow muscle fibers might play an important role in sustaining neutral alignment of the lower extremity.
authors.affiliation: Department of Molecular Predictive Medicine and Sport Science, Kyorin University, School of Medicine, 6-20-2, Shinkawa, Mitaka, Tokyo 181-8611, Japan. yhitomi@kyorin-u.ac.jp
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Hitomi
authors.forename: Takako
authors.initials: T
authors.lastname: Kizaki
authors.forename: Sumiko
authors.initials: S
authors.lastname: Watanabe
authors.forename: George
authors.initials: G
authors.lastname: Matsumura
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Fujioka
authors.forename: Shukoh
authors.initials: S
authors.lastname: Haga
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Izawa
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Taniguchi
authors.forename: Hideki
authors.initials: H
authors.lastname: Ohno
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D006614:Hindlimb / Q000201:enzymology*; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D018657:Muscle Fibers, Slow-Twitch / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000201:enzymology*; D009218:Myosins / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits; D051381:Rats
chemical_list: D009218:Myosins