NPPA and pulmonary arterial hypertension: In this study, by using HE and WGA staining, we found that the wall thickness of the RV, the cross-sectional area, and perimeter of individual cardiomyocyte significantly increased in rats exposed to hypoxia for 4 weeks, accompanied by an increase in the mRNA expressions of ANP and BNP in the RV tissue, confirmed the role of myocardial hypertrophy in RV remodeling in hypoxic PAH.