The Japanese Journal of Physiology
Print ISSN : 0021-521X
Regular Papers
Vascular Endothelial Growth Factor, Capillarization, and Function of the Rat Plantaris Muscle at the Onset of Hypertrophy
Hans DegensJo Ann MooreStephen E. Alway
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2003 Volume 53 Issue 3 Pages 181-191


Capillary proliferation occurs during compensatory hypertrophy. We investigated whether the expression of vascular endothelial growth factor (VEGF) is elevated at the onset of hypertrophy when capillary proliferation is minimal, and whether muscle damage as assessed by muscle force deficits, may occur at the onset of hypertrophy. To investigate this, we induced in 9-month-old rats, under isoflurane anesthesia, hypertrophy of the left plantaris muscle by denervation of the gastrocnemius and soleus muscles. Capillarization was investigated in both the deep (oxidative) and the superficial (glycolytic) regions of the plantaris muscle. After 2 weeks, muscle mass had increased by 16% (plt;0.01), which was not accompanied by increases in fiber size. The maximal tetanic force (P0) and specific tension (P0·g−1 or P0·cm2) and twitch characteristics were unaltered, and fatigue resistance of the overloaded muscle was improved (plt;0.05). However, the myosin heavy chain composition was unaltered. Capillary proliferation was not yet evident, but VEGF mRNA and protein levels were elevated 1.5- and 8-fold, respectively (plt;0.05). We concluded that the normal specific tension and the elevated VEGF expression after 2 weeks of overload indicate (1) an absence of or minimal muscle damage at this early time point, and (2) that elevated VEGF expression precedes and is involved in capillary proliferation that occurs during the later stages of compensatory hypertrophy.

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© 2003 by The Physiological Society of Japan
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