## 2 Materials and Methods
For the determination of plasma levels of ET-1, they used the radioimmunological assay. Since they could not directly measure NO because of its short half-life, they measured plasma nitrates (NOx) whose main source during exercise turns out to be the NO. They then performed a limited physical symptom test and then calculated the NO/ET-1 ratio. A lower ratio was obtained in the group of people with coronary disease (1.2 +/\(-\) 1.1 vs. 2.7 +/\(-\) 2.2, \(p\) < 0.01), and a sensitivity and specificity of the NO/ET-1 ratio was found in indicating coronary heart disease of 90% and 80% respectively, compared to 80% and 78% found using the evaluation of the substandard segment ST. Therefore, the NO/ET-1 ratio is a useful biological marker of coronary heart disease. It should be noted that, according to the above, exercise is able to change this ratio. Among other things, we have already seen how it is able to decrease the ET-1 and increase the expression and activity of Enos. Therefore, sport, through the modifications induced on 'E., protects from atherosclerosis. There is an anti-pro-thrombotic balance in which E is involved. In fact, the release, by the E., of t-PA (tissue activator of plasminogen, considered the primary defense mechanism against thrombogenesis [33] and obesity) is associated with an increased risk of atherosclerotic events [34]. The authors who have approached this research have demonstrated the influence of obesity on t-PA release capacity as well as the effects of regular aerobic exercise [35]. Subject were randomized. Hence, 66 sedentary adults: 28 with BMI < 25, 22 with 25 < BMI < 30, 16 with BMI > 30. The release capacity of t-PA was evaluated in response to bradykinin-related infusion and SNP (sodium nitroprusside). A second mixed group, between obese and overweight, of 17 adults who had completed a three-month aerobic training program. In the 66 sedentary subjects, t-PA release was 45% lower (_p_ < 0.01), in both the obese and overweight groups, compared to the normal weight group. The mixed group of 17, on the other hand, after three months of training, showed an almost double release capacity (from 37.1 +/\(-\) 4.9 ng/100 mL tissue/min before training, to 65.4 +/\(-\) 6.3 ng/100 mL tissue/min after training \(p\) < 0.01), which was effective with that of sedentary. These results indicate that regular physical activity can correct endothelial dysfunction present in subjects with BMI > 25 and thereby reduce their atherosclerotic risk. According to our studies, in agreement with other research groups in this field, the adoption of a lifestyle has been shown to be able not only to significantly reduce the risk of developing diabetes, but also to prevent important complications that can be fatal for the patient's life or in any case strongly disabling [36]. Another published paper [21] allowed us to assess the relationship between long-term physical activity, plasma antioxidant capacity, and endothelial function in young and non-young subjects. Four groups were then compared: one consisting of 16 young athletes, one of 16 older athletes, a group of young sedentary, and finally the group of older sedentary subjects, all in good health. Hence, as a reference, in the brachial artery, they measured, by means of high-resolution ultrasound, the E.-dependent vasodilation (VED) and the E.-independent (VEI, caused by trinitroglycerin) and plasma capacity, to eliminate peroxylic and hydroxyl radicals. These are the results: the older sedentary group reported the lowest values, on both sides (VED, antioxidant capacity), with significant differences compared to the other three groups, which were substantially homogeneous. The authors conclude that sedentary ageing increases oxidative stress and, for this and other reasons, worsens endothelial function. However, regular physical activity can reverse this course.