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. This evidence concerns the gene NPPB and pulmonary arterial hypertension.