## 2 Materials and Methods  
An extensive scientific literature review was conducted using Scopus, Pubmed, and GoogleScholar databases. We selected 40 publications. After approximately 25 years of research, the endothelium is still of great interest to hundreds of researchers, proving its complexity and importance. The endothelium releases various vasoactive factors. see Figure 1. These can be vasodilatory factors see Figure 2 such as nitric oxide (NO), prostacyclin (PGI2), and endothelium derived hyperpolarizing factor (EDHF), or vasoconstrificators, such as thromboxane (TXA2) and endothelin-1 (ET-1) [22]. The NO has anti-thrombotic action, while the ET-1 has pro-thrombotic action [23]. Based on these and other properties and after years of research, E. has been called into question as an \"organ\" involved in regulating blood flow in general [24] and coronary and renal [25] in particular, in regulating blood pressure and in the pathogenesis of certain cardiovascular diseases, such as essential arterial hypertension, heart failure, atherosclerosis, and ischemic heart disease. Can sport intervene in all this by changing the synthesis of its mediators and reprogramming it? There is some research on rats and people. In the first study, carried out by researchers of the Cardiological Division of the University Magna Greccia of Catanzaro [26], in two groups of rats (one group subjected to exercise, the other sedentary), the consequences of the use of a stent or vascular damage induced by a balloon catheter angioplasty were evaluated. The authors saw that the arteries isolated from the group of trained rats showed higher levels of Enos [27], and in addition had less neointimal hyperplasia and earlier orientation in the case of stent use, while they showed a lower probability of ristenosi, a lower platelet aggregation, and a more favorable vascular remodeling in the case of insult induced by angioplasty. In a third group, the administration of monomethyl-L-arginine, inhibitor of the synthesis of NO [20], prevented the expression of the benefits observed in trained rats. It should  
Figure 1: Endothelial nitric oxide production and it actions in the vascular smooth muscle cell. Figure 2: Endothelial function and vascular structure performed in different vascular beds. be noted that these results agree with the physiology data recalled at the beginning of this paragraph. Moreover, before illustrating the next study, it is necessary to remember that the role of E. is mandatory [28] for the vasodilation induced by Ach (acetylcholine) [29], see Figure 3.  
In 2003, other researchers [30] proposed to verify if the activity of E. is greater in athletes than in less trained subjects. Based on the assumption that endothelial activity (see Scheme 1) can be tested by comparing the level of vasodilation induced by an E.-dependent vasodilator (Ach) to that induced by an E.-independent vasodilator (sodium nitroprusside, SNP), using the LDF (laser doppler fluxometry) technique, the authors measured the cutaneous perfusion induced by Ach in a group of athletes and a group of less trained people. Response to Ach was found to be 1.6 times greater in athletes than with \(p<0.05\) (therefore a statistically significant difference), while response to SNP was not different,  
Figure 3: Endothelium-dependent vasodilation. the study concluded that E. is more active in athletes. Another study carried out [31] in 28 healthy subjects calculated ET-1 concentrations before and after a cycloergometer test using the ELISA method: the mean concentrations were lower after the test (_p_ < 0.01, highly significant difference). In different recent works authors questioned whether the NO/ET-1 ratio was useful for diagnosing coronary artery disease, given that it was recently considered crucial in the early stages of atheogenesis, as well as the maintenance and progression of plaque [32]. Hence, 63 people were randomized, 38 with normal coronary and average age of 60 years, 25 suffering from stable angina and average age of 69 years.