HMOX1 and pulmonary arterial hypertension: Here we found an additive increase in HO-1 mRNA expression by PETN in lung tissue of PAH rats providing an attractive explanation for the beneficial effects of PETN therapy on vascular and pulmonary oxidative stress parameters and subsequent improvement of endothelial function in pulmonary arteries, PAP, and morphological changes (heart/body, lung/body ratio) observed in MCT-treated animals.