[Effects of hypoxia alone or exercise combined on capillarization of rat gastrocnemius muscle and its mechanism].
ABSTRACT To study the effects of hypoxia and hypoxia-combined-exercise on capillary density and vascular endothelial growth factor (VEGF) and its receptor KDR of skeletal muscle in rats.
Myosin-ATPase histochemistry was used to assay the size and capillary density of skeletal muscle. VEGF and its receptor KDR were studied by immunohistochemistry.
Five-week hypoxia (simulated 5,000 m altitude) resulted in a decrease in cross-sectional area of skeletal muscle fiber and an increase in capillary density (CD), but the capillary/fiber ratio (C/F) remained unchanged. After 5-week-exercise at high altitude (1 h/d, 6 d/w), the muscle fibers did not undergo atrophy. At the same time, CD and C/F were increased. VEGF protein was found primarily in the matrix between muscle fibers; VEGF receptor-KDR was shown mainly in endothelial cells of capillary. VEGF was more strongly stained in the skeletal muscle of hypoxia-combined-exercise rats than the other two groups.
Hypoxia itself can not induce neovascularization, while hypoxia-combined-exercise rats show capillary proliferation in skeletal muscle. VEGF and its receptor might play roles in this process.