Expression of vascular endothelial growth factor and its receptors in heart tissue following short-term swimming training

The goal of this study was to investigate the expression of angiogenesis-associated genes in heart tissue in response to short-term exercise. Twenty-six male mice were divided randomly into sedentary and swimming-trained groups. Mice swam without a load for 50 min/day. Swimming training was carried out in six 50-min training sessions over a 9-day period. The mRNA for angiogenesis-related factors, including hypoxia inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), fms-like tyrosine kinase (Flt-1), and kinase insert domain-containing receptor/fetal liver kinase-1 (KDR/Flk-1), was analyzed using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Also, semi-quantitative RT-PCR was carried out to further determine which of the VEGF isoforms changed in heart tissue. Swimming training significantly increased HIF-1α (1.5-fold), VEGF (2.2-fold), Flt-1 (1.9-fold), and KDR/Flk-1 (2.4-fold) mRNA levels. Also, VEGF188 and VEGF164 mRNA levels were elevated but their relative abundance was the same as in sedentary mice. These results suggest that short-term swimming training stimulates not only the expression of VEGF mRNA, which may be due to increases in VEGF188 and VEGF164 mRNAs, but also Flt-1 and KDR/Flk-1 mRNAs in the heart.