NO is produced by the enzymatic catalysis of endothelial nitric oxide synthase (eNOS), and previous studies in the pulmonary hypertension rat model have verified the involvement of NO in regulating eNOS phosphorylation and PI3K/AKT/eNOS and cGMP-PKG signaling pathways [40, 41]. This evidence concerns the gene AKT1 and pulmonary arterial hypertension.