In the present study, it has been demonstrated that OS improved major characteristic pathological features of MCT-induced PH in rats, including increased RVSP, right ventricular hypertrophy, echocardiographic parameters (increased RVoTD/AoD and reduced PAAT/ET), altered oxidative stress markers, increased expression of lung Nox-1 protein, proapoptotic changes in right ventricle, and most importantly, increased thickness of distal arterioles (of diameter <100 μm). This evidence concerns the gene NOX1 and Right ventricular hypertrophy.