EDN1 and pulmonary arterial hypertension: Even though the ETBRs are also required for vasoconstriction and collagen synthesis, and ETBRs were upregulated in fibrotic-related diseases, such as scleroderma-associated fibrotic lung disease [44] and pulmonary arterial hypertension [45], our present study revealed that the ETBRs did not involve in the profibrotic effects of ET-1 in human cardiac fibroblasts.