EDN1 and Hypertension: While early studies on the role of endothelial cells in SSHTN explored how the loss of vasodilatory function due to NO impairment in endothelial cells impacted hypertension, d’Uscio et al. explored how endothelin-1 (ET-1), a potent vasoconstricting peptide produced mainly by endothelial cells, regulates vascular tone in Dahl SS rats, finding that the salt sensitive animals had increased plasma ET-1 levels relative to controls (d'Uscio et al., 1997).