The ET-1 concentration in pulmonary arterial supernatants in hypoxemic COPD group was significantly higher than that in control group and nonhypoxemic COPD group (6.16 ± 0.83 vs. 1.43 ± 0.26 and 3.42 ± 0.63 fmol/mL; P < 0.001 and P < 0.05, respectively) (Table 2). The gene discussed is EDN1; the disease is chronic obstructive pulmonary disease.