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Skeletal muscle capillary geometry: adaptation to chronic hypoxia
D C Poole1, O Mathieu-Costello
1Department of Medicine, University of California, San Diego, La Jolla 92093.
Respiration Physiology
|July 1, 1989
Summary
Chronic hypoxia exposure at 3800m did not alter capillary tortuosity or surface area in rat leg muscles. This suggests altitude adaptation does not enhance blood-tissue exchange via capillary structural changes.
Area of Science:
- Physiology
- Altitude Physiology
- Vascular Biology
Background:
- Capillary structure, including length and surface area, is crucial for gas and metabolite exchange.
- Chronic hypoxia is hypothesized to increase capillary tortuosity, potentially enhancing blood-tissue transfer.
- Quantifying capillary orientation changes under sustained hypoxia is essential for understanding physiological adaptations.
Purpose of the Study:
- To rigorously quantify the degree of capillary orientation and tortuosity in rat skeletal muscles after prolonged exposure to high altitude.
- To determine if chronic hypoxia alters capillary length per volume of muscle fiber (Jv(c,f)) through changes in tortuosity, independent of angiogenesis.
Main Methods:
- Female rats were exposed to 3800m altitude for 5 months.
- Capillary tortuosity and Jv(c,f) were measured in M. Soleus and M. Gastrocnemius using transverse and longitudinal sections.
- Measurements were compared to weight-matched control rats at sea level.
Main Results:
- Neither capillary density nor capillary-to-fiber ratio changed significantly after altitude exposure.
- Capillary tortuosity was dependent on sarcomere length but unaffected by chronic hypoxia.
- Capillary length per volume of muscle fiber and mean capillary diameter remained unchanged.
Conclusions:
- Chronic exposure to 3800m altitude does not induce changes in capillary tortuosity in the studied rat muscles.
- The structural parameters governing blood-tissue exchange, specifically capillary surface area and length per fiber volume, are not altered by prolonged high-altitude exposure in these muscles.