Skeletal muscle adaptations to microgravity exposure in the mouse.
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.
Harrison
B C
BC
Department of Kinesiology, University of Colorado, Boulder, CO 80309, USA.
Allen
D L
DL
Girten
B
B
Stodieck
L S
LS
Kostenuik
P J
PJ
Bateman
T A
TA
Morony
S
S
Lacey
D
D
Leinwand
L A
LA
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*
D002950:Citrate (si)-Synthase; D018995:Myosin Heavy Chains