ABSTRACT: The aim of the present study was to explore the effects of continuous and intermittent exercise on the thoracic aortic vasoreactivity and free radical metabolism in rats fed with a high-fat diet (HD). Sprague-Dawley (SD) rats were randomly divided into four groups (n=8, each group): Conventional diet (CD), HD, HD with continuous exercise (HCE) and HD with intermittent exercise (HIE). HCE rats swam once/day for 90 min; HIE rats performed swimming exercises 3 times/day, 30 min each time with an interval of 4 h. In these two groups, the exercise was conducted 5 days a week for 8 weeks. Rats in the CD and HD groups were fed without swimming training. At the end of the exercise, all the rats were sacrificed and the blood, thoracic aorta and myocardium were collected immediately. The thoracic aortic vasoreactivity, the plasma total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), superoxide dismutase (SOD), malondialdehyde (MDA) and vascular endothelial nitric oxide synthase (eNOS) gene expression were measured. Compared to the control group, in the HD group the enhanced contractile response of the thoracic aortic rings to noradrenaline (NA) was observed (P<0.01). The levels of TC and LDL (P<0.01) were also increased in serum while the HDL level was reduced without statistical significance. In addition, the MDA content was upregulated in the myocardium, but the SOD level decreased (P<0.01). Furthermore, the expression of vascular eNOS mRNA was reduced (P<0.01). However, following the exercise the contraction of the thoracic aorta vascular rings to NA was reduced in the HCE and HIE groups (P<0.01), and the decreased contractile response was more evident in the HIE group compared to the HCE group (P<0.01). Additionally, in the HCE group the level of TG (P<0.01) was decreased, while the HDL (P<0.01) level was increased. Although the reduction of the TC and LDL level was also observed there was no significant difference compared to the HD group. In the HIE group, the TG, TC and LDL were downregulated while the HDL was enhanced (P<0.01). The TC and LDL levels were decreased more than those of the HCE group; however, there was no significant difference in the TG and HDL levels between these two groups; additionally, in these two exercise groups, the MDA level was decreased in the myocardium (P<0.01) while the SOD level was increased (P<0.01). Furthermore, the expression of eNOS was upregulated (P<0.01), but the increase was much more in the HIE group than that in the HCE group. In conclusion, exercise may attenuate the aggravated contraction induced by NA and improve the activity of the thoracic aorta in obese rats, which may be associated with enhanced antioxidant enzyme activity and reduced free radical generating. Additionally, intermittent exercise is better than the continuous exercise in improving the thoracic aorta vasoreactivity.
