Effect of endurance training on angiogenic activity in skeletal muscles.

The effect of endurance training on angiogenic activity in skeletal muscle was investigated using cell culture. The exercised rats were trained on a rodent treadmill, 5 days a week for 9 weeks. After the training program, a significant increase (7.8%) in mass was found in soleus muscle (MS), although we noted no apparent increase in gastrocnemius muscle and extensor digitorum longus muscle. The extracts from all the muscles (especially from the MS) of trained rats considerably increased the capillary growth in an in vitro angiogenesis model, in which microvascular fragments and myofibroblastic (Mf) cells isolated from lipid tissues were grown in co-culture. In addition, the extract from the MS of trained rats increased the DNA synthesis and growth of bovine capillary endothelial (BCE) cells, although the extract did not stimulate the growth of Mf cells. Moreover, the extract from the MS of trained rats notably enhanced the activity of plasminogen activator in the conditioned medium of BCE cells compared with that of sedentary rats. On the other hand, extracts from the MS of both sedentary and trained rats increased the synthesis of collagen by Mf cells and metalloproteinase activity in the conditioned medium of BCE cells to the same degree. These results suggest that endurance training increases the angiogenic activity in skeletal muscles.