Intensity of swimming exercise influences aortic reactivity in rats

Exercise is known to cause a vasodilatory response; however, the correlation between the vasorelaxant response and different training intensities has not been investigated. Therefore, this study evaluated the vascular reactivity and lipid peroxidation after different intensities of swimming exercise in rats. Male Wistar rats (aged 8 weeks; 250-300 g) underwent forced swimming for 1 h whilst tied to loads of 3, 4, 5, 6, and 8% of their body weight, respectively (groups G3, G4, G5, G6 and G8, respectively; n=5 each). Immediately after the test, the aorta was removed and suspended in an organ bath. Cumulative relaxation in response to acetylcholine (10(-12)-10(-4) M) and contraction in response to phenylephrine (10(-12)-10(-5) M) were measured. Oxidative stress was estimated by determining malondialdehyde concentration. The percentages of aorta relaxation were significantly higher in G3 (7.9 +/- 0.20), G4 (7.8 +/- 0.29), and G5 (7.9 +/- 0.21), compared to the control group (7.2 +/- 0.04), while relaxation in the G6 (7.4 +/- 0.25) and G8 (7.0 +/- 0.06) groups was similar to the control group. In contrast, the percentage of contraction was significantly higher in G6 (8.8 +/- 0.1) and G8 (9.7 +/- 0.29) compared to the control (7.1 +/- 0.1), G3 (7.3 +/- 0.2), G4 (7.2 +/- 0.1) and G5 (7.2 +/- 0.2%) groups. Lipid peroxidation levels in the aorta were similar to control levels in G3, G4 and G5, but higher in G6 and G8, and significantly higher in G8 (one-way ANOVA). These results indicate a reduction in vasorelaxing activity and an increase in contractile activity in rat aortas after high-intensity exercise, followed by an increase in lipid peroxidation.