New insights into the vascular mechanisms underlying the beneficial effect of swimming training on the endothelial vasodilator function in apolipoprotein E-deficient mice

The antiatherogenic role of exercise is poorly understood. We examined the swimming exercise-induced vascular mechanisms which enhance the endothelial vasodilator function in apoE−/− mice. Male apoE−/− mice treated for 9 weeks with a lipid-rich diet were divided into two groups: the exercise group (apoE−/− X), which underwent a 9-week swimming protocol (50 min/day; 5 days/week) and the sedentary group (apoE−/− S). C57BL/6 mice were used as the control group. Atherosclerotic lesions in the aortic roots were significantly reduced in apoE−/− X compared to apoE−/− S. Relaxation to acetylcholine was improved in apoE−/− X as compared to apoE−/− S and control mice with Emax and pD2 values significantly higher. pD2 values in response to papaverine were higher in apoE−/− X than in the other groups. Relaxation in response to A23187 and DEA-NONOate were similar. These findings suggest that swimming training may increase the sensitivity of relaxation to acetylcholine, which in turn activates acetylcholine-mediated signaling pathways leading to increased NO bioactivity. Swimming may also prolong the signaling actions of NO by stimulating the sensitivity of vascular smooth muscle cells to cyclic nucleotides. These appear to be the key mechanisms underlying the improvement of the NO-cGMP pathway in exercised apoE−/− mice.