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.