Angiogenic growth factor mRNA responses in muscle to a single bout of exercise

Abstract

A major adaptation to exercise is new capillary formation in skeletal muscle. On the basis of angiogenesis in tumors and during development, several angiogenic growth factors may be involved, including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and transforming growth factor-beta 1 (TGF-beta 1). In 9-wk-old female Wistar rats, mRNA expression for these three growth factors in gastrocnemius muscle was examined by quantitative Northern analysis after a single 1-h run at 15 or 20 m/min at 10 degrees incline in room air. A third group ran at 15 m/min in 12% O2, and resting control groups were included at inspired O2 fractions of 0.21 and 0.12. Exercise significantly increased mRNA levels two- to fourfold, which was evident over the first 4 h postexercise; by 8 and 24 h, mRNA levels returned to baseline. For all three factors, mRNA levels were significantly higher after exercise at 20 than at 15 m/min. Hypoxia at rest doubled VEGF and TGF-beta 1 message but had no effect on bFGF. Hypoxic exercise further raised VEGF mRNA levels but had no effect on the other factors. We suggest that VEGF, bFGF, and TGF-beta 1 may be involved in the angiogenic response to exercise and that reduced intracellular PO2 (as occurs during normoxic exercise) may be part of the stimulus to such growth factor production.

Effect of eccentric exercise on the healing process of injured patellar tendon in rats

“…The VEGF mRNA response to increases in exercise intensity has been shown previously. 7,8 Exercise is essential to accelerate neovascularization and thereby elicit a healing response in the injured tendon. Increased levels of angiogenic growth factors, such as VEGF, Fig.…”

Selective long-term electrical stimulation of fast glycolytic fibres increases capillary supply but not oxidative enzyme activity in rat skeletal muscles

“…Increases in capillary supply preceding the changes in oxidative enzymes were described previously (Pette et al 1973;Brown et al 1976), and were confirmed more recently (Skorjanc et al 1998) using different stimulation regimes than those used in the present study. It is normally assumed that increased activity of oxidative enzymes in muscles of endurance-trained animals is a sign of hypoxia which triggers capillary growth, possibly via vascular endothelial growth factor (VEGF; Breen et al 1996). This hypothesis would seemingly be supported by previous experiments showing that, when all fibres were stimulated for 2 days, capillary density was higher than in control muscles in the vicinity of fast glycolytic fibres while there was, at this early stage, no change in the capillary supply in the vicinity of the highly oxidative fibres (Hudlick a et al 1982).…”

Diaphragmatic angiogenic growth factor mRNA responses to increased ventilation caused by hypoxia and hypercapnia

“…It has been shown that a single, 1-h bout of exercise of normal skeletal muscles increases the messenger ribonucleic acid (mRNA) levels of VEGF, bFGF and TGF-b 1 [9] (more so in hypoxia for VEGF, in particular). In addition, electrical stimulation increases VEGF levels [10].…”