Skeletal muscle adaptations to microgravity exposure in the mouse

J Appl Physiol (1985). 2003 Dec;95(6):2462-70. doi: 10.1152/japplphysiol.00603.2003. Epub 2003 Jul 25.


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.

MeSH terms

  • Adaptation, Physiological / physiology*
  • Animals
  • Body Weight / physiology
  • Citrate (si)-Synthase / metabolism
  • Female
  • Heart / anatomy & histology
  • Immunohistochemistry
  • Isomerism
  • Mice
  • Mice, Inbred C57BL
  • Muscle Fibers, Skeletal / ultrastructure
  • Muscle, Skeletal / cytology
  • Muscle, Skeletal / metabolism
  • Muscle, Skeletal / physiology*
  • Myosin Heavy Chains / biosynthesis
  • Myosin Heavy Chains / metabolism
  • Organ Size / physiology
  • Oxidation-Reduction
  • Space Flight
  • Weightlessness / adverse effects*


  • Citrate (si)-Synthase
  • Myosin Heavy Chains