Mechanism of exercise-induced angiogenesis in rat hippocampi

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It was studied the effects of endurance swim training on the angiogenesis, and the gene expression of hypoxic induced factor-2a (HIF-2a) and vascular endotherial growth factor (VEGF) in rat hippocampi. One control group of 12 rats took a daily bath for 2 h. An unloaded group of 12 rats swam daily for 2 h with no sinker. A loaded group of 12 rats were subjected to daily 2-h swimming with a sinker of 1.5% of own body weight attached to the neck of rat. The rat hippocampi were prepared after 1-, 3-, and 6-weeks training. A half of hippocampal samples in each group was subjected to the morphometrical analysis of blood vessels. The remaining samples were carried on the quantitative analysis of mRNA of HIF-2a, VEGF, and b-action of internal control. In the loaded group, the swim training increased the frequency of small capillary with 5-6 mm in diameter and the mean value of total capillary length per tissue volume (CL). Also, it decreased the mean diameter of capillaries and mean distance between capillaries (Cd). The unloaded group had the largest CL value andmean area of total capillaries, and smaller value of Cd in comparison with the control group. The frequency of capillaries with 6-7 mm diameter increased. Compared with control group, the percentage of HIF-2a mRNA was significantly higher by about 50% of control value in the unloaded group after 1 week. The loaded group showed the higher percentages after 1, 3, and 6 weeks, respectively as 1.8-, 1.75-, and 1.5-fold of control values. This suggests that hypoxic condition in hippocampus was more sever in loaded group than in unloaded group. The training enhanced the expression of VEGF mRNA. In the unloaded group, an amount of VEGF mRNA was higher than control group after 1-and 3-weeks training. Amount of VEGF mRNA was higher in loaded group at weeks 1,3, and 6 than that in control.