EDNRA and pulmonary arterial hypertension: Upregulation of vasoconstrictive mediators in PAECs and PASMCs, such as endothelin-1 and endothelin receptor A (ETA), which is accompanied by downregulation of vasodilatory mediators such as NO, prostacyclin (PGI2), endothelium-derived hyperpolarizing factor (EDHF), or prostaglandin receptors (DPs, EPs, FP, IP, or TP), is one example of the imbalance of GPCR-expression that contributes to the increased pulmonary vascular resistance in PAH patients [126].