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Rat soleus muscle ultrastructure after hindlimb suspension
D Desplanches1, S R Kayar, B Sempore
1Laboratoire de Physiologie, Faculté de Médecine, URA 1341 Centre National de la Recherche Scientifique, Lyon, France.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 1, 1990
Summary
Tail suspension caused significant soleus muscle atrophy in rats, reducing muscle mass and fiber size. Despite these changes, the muscle
Area of Science:
- Muscle physiology and cellular biology
- Skeletal muscle adaptation to unloading
Background:
- Muscle atrophy is a significant concern in conditions of unloading, such as spaceflight or bed rest.
- Understanding the cellular mechanisms underlying muscle atrophy is crucial for developing countermeasures.
Purpose of the Study:
- To investigate the ultrastructural changes in rat soleus muscle after a 5-week tail-suspension period.
- To quantify the effects of hypokinesia on muscle mass, fiber size, capillary supply, and mitochondrial distribution.
Main Methods:
- Quantitative electron microscopy was employed to analyze soleus muscle samples.
- Measurements included muscle mass, fiber cross-sectional area, capillary-to-fiber ratio, capillary density, and mitochondrial and myofibril volume densities.
Main Results:
- A 60% decline in soleus muscle mass and a 75% decrease in mean fiber cross-sectional area were observed.
- Capillary density increased by 148%, while the capillary-to-fiber ratio decreased by 37%.
- Total mitochondrial volume density remained unchanged, but a shift from subsarcolemmal to interfibrillar mitochondria occurred, with increased satellite cell density suggesting regeneration.
Conclusions:
- Tail-suspension-induced soleus atrophy significantly reduces muscle volume and fiber size.
- Ultrastructural composition, including mitochondrial content, is relatively preserved despite substantial atrophy.
- Evidence of muscle regeneration was suggested by increased satellite cell volume density.