EDN1 and pulmonary arterial hypertension: In the COPD rat model test, it was found that DZXXI can reduce rat hematocrit, reduce the expression of pulmonary arteriole type collagen and endothelin 1 (ET-1), reduce pulmonary vascular resistance, thereby inhibiting pulmonary vasoconstriction and remodeling, relieving pulmonary hypertension and preventing the formation of hypoxic pulmonary hypertension (Zhang et al., 2009), which is also consistent with the previous literature reports of clinical therapeutic effects.