Adaptation of rat gastrocnemius muscles to 2 weeks of centrifugation: myofibers and extracellular matrix.
BACKGROUND
The effect of 2 wk of exposure to centrifugation (2G) on gastrocnemius muscles of rats was investigated by morphometric and computer-assisted image analysis of muscle fiber areas and non-contractile tissue components (extracellular matrix).


RESULTS
Muscle atrophy was seen in the myofibers from 2G rats which had decreased in cross-sectional area by 26%. In contrast, the non-contractile tissue component actually increased by 13%. These results were compared with soleus muscle atrophy seen following 2 wk of unloading by tail-suspension. In all cases, the extracellular matrix increased in proportion to the decrease in fiber area. A theoretical model was developed to assess the effect of changes in myofiber cross-sectional area on the relative content of the extracellular matrix. The experimental results from both rat gastrocnemius and soleus muscles were consistent with the model with slight variations due to the known differences in connective tissue content of different muscles in the rat.


CONCLUSIONS
Thus, the gastrocnemius muscle atrophy seen after 2 wk of centrifugation results from loss of contractile and other myofiber specific proteins while the extracellular matrix remains relatively constant. The loss in myofiber content was greater than expected from changes in muscle wet weight and more than required to adapt to a decrease in body weight.
Stauber
W T
WT
Department of Physiology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown 26506-9229, USA.
Miller
G R
GR
Grimmett
J G
JG
D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D002498:Centrifugation / Q000009:adverse effects*; D005109:Extracellular Matrix / Q000502:physiology* / Q000648:ultrastructure*; D018471:Hypergravity / Q000009:adverse effects; D008962:Models, Theoretical; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology* / Q000648:ultrastructure*; D009133:Muscular Atrophy / Q000209:etiology* / Q000473:pathology* / Q000503:physiopathology; D009210:Myofibrils / Q000502:physiology* / Q000648:ultrastructure*; D009929:Organ Size; D051381:Rats; D013026:Space Flight; D013997:Time Factors; D015431:Weight Loss; D016474:Weight-Bearing