As observed in our study, among these four enzymes, only xanthine oxidase (XO) produced ROS, a result in line with the work by Landmesser35, who reported a marked increase in endothelial XO levels and in XO-dependent endothelial superoxide production after AGII administration, suggesting that AGII-activated XO is a major superoxide source in coronary diseases resulting from ED. This evidence concerns the gene XDH and coronary artery disorder.