EDN1 and pulmonary arterial hypertension: There was also an approximately 2-fold-increase in the concentration of 6-keto-PGF1α in plasma 4 weeks post MCT, as compared to Control (Fig. 2c) as well as increase plasma concentration of ET-1, which is considered a reliable biomarker of PAH progression (ET-1 in plasma: 91.42 ± 7.63 and 214.95 ± 27.87 vs 47.95 ± 2.67 ng/ml at 2 weeks and 4 weeks for post-MCT and Control groups, respectively, P < 0.05) (Fig. 2d).