title: Skeletal muscle adaptations to microgravity exposure in the mouse.
abstract: To investigate the effects of microgravity on murine skeletal muscle fiber size, muscle contractile protein, and enzymatic activity, female C57BL/6J mice, aged 64 days, were divided into animal enclosure module (AEM) ground control and spaceflight (SF) treatment groups. SF animals were flown on the space shuttle Endeavour (STS-108/UF-1) and subjected to approximately 11 days and 19 h of microgravity. Immunohistochemical analysis of muscle fiber cross-sectional area revealed that, in each of the muscles analyzed, mean muscle fiber cross-sectional area was significantly reduced (P < 0.0001) for all fiber types for SF vs. AEM control. In the soleus, immunohistochemical analysis of myosin heavy chain (MHC) isoform expression revealed a significant increase in the percentage of muscle fibers expressing MHC IIx and MHC IIb (P < 0.05). For the gastrocnemius and plantaris, no significant changes in MHC isoform expression were observed. For the muscles analyzed, no alterations in MHC I or MHC IIa protein expression were observed. Enzymatic analysis of the gastrocnemius revealed a significant decrease in citrate synthase activity in SF vs. AEM control.
authors.affiliation: Department of Kinesiology, University of Colorado, Boulder, CO 80309, USA.
authors.forename: B C
authors.initials: BC
authors.lastname: Harrison
authors.forename: D L
authors.initials: DL
authors.lastname: Allen
authors.forename: B
authors.initials: B
authors.lastname: Girten
authors.forename: L S
authors.initials: LS
authors.lastname: Stodieck
authors.forename: P J
authors.initials: PJ
authors.lastname: Kostenuik
authors.forename: T A
authors.initials: TA
authors.lastname: Bateman
authors.forename: S
authors.initials: S
authors.lastname: Morony
authors.forename: D
authors.initials: D
authors.lastname: Lacey
authors.forename: L A
authors.initials: LA
authors.lastname: Leinwand
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001835:Body Weight / Q000502:physiology; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005260:Female; D006321:Heart / Q000033:anatomy & histology; D007150:Immunohistochemistry; D007536:Isomerism; D051379:Mice; D008810:Mice, Inbred C57BL; D018485:Muscle Fibers, Skeletal / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000096:biosynthesis / Q000378:metabolism; D009929:Organ Size / Q000502:physiology; D010084:Oxidation-Reduction; D013026:Space Flight; D014893:Weightlessness / Q000009:adverse effects*
chemical_list: D002950:Citrate (si)-Synthase; D018995:Myosin Heavy Chains