Modulatory Effects of Swimming Training on Hypoxia-Induced Factors in Heart Tissue of Rats Exposed to Chronic Stress

 Monitoring cardiac, metabolic, neurological, and aging responses to stressors is critical. This study aimed to investigate the effect of swimming training on HIF-1α and vascular endothelial growth factor (VEGF) levels in heart tissue of rats exposed to chronic stress.

 To this end, 30 male Wistar rats (age: 10 - 12 weeks, weight: 220 ± 20 g) were randomly divided into five equal groups of six rats as follows: (1) Con (no treatment for 10 weeks); (2) CS + ST (4 weeks of stress, 4 weeks of swimming); (3) ST (4 weeks of swimming); (4) CS (4 weeks of stress); (5) CS-time (4 weeks of stress, 6 weeks of no treatment). Anxiety-like behaviors were measured by an open field test. Heart tissue was immunohistochemically assessed for HIF-1α expression using a polyclonal antibody. Vascular endothelial growth factor protein levels were also determined using western blot analysis. To analyze the data, Kolmogorov-Smirnov, One-way ANOVA, and Tukey’s post hoc tests were used, and P ≤ 0.05 was considered statistically significant.

 The results showed that chronic mild stress (CMS) significantly decreased the HIF-1α expression in heart tissue in CS and CS-time groups (P < 0.05). Furthermore, the result revealed that swimming training significantly increased the level of HIF-1α expression in heart tissue in ST and CS + ST groups (P < 0.05). Although swimming training increased HIF-1α levels in the CS + ST group after a period of four weeks of CMS, these increases were smaller than those observed in ST and control groups (P < 0.05). The results from the One-way ANOVA test also demonstrated that the CMS significantly downregulated the VEGF expression in heart tissue in CS and CS-time groups, whereas swimming training significantly increased its level in ST and CS + ST groups (P < 0.05). Although swimming training increased VEGF levels in the CS + ST group after a period of four weeks of CMS, these increases were smaller than those detected in ST and control groups.

 Although chronic mild stress had the potential to reduce hypoxia-induced factors in heart tissue, swimming training modified these factors.