EDN1 and COVID-19: Several vasoconstrictors and vasodilators are produced by the endothelium, such as nitric oxide (NO), endothelin-1 (ET-1), and also angiotensin-2 (Ang 2), which regulates vasomotor tone, inflammatory cells, and thrombosis and COVID-19-mediated irregularities in these vasoconstrictors and vasodilators may worsen ARDS.