Importantly, an examination of hyperpermeability in the hypoxia-SU5416 rat model of PAH localized impaired endothelial barrier function to perivascular fluid cuffs around extra alveolar vessels and not the alveolar capillaries (50), a pattern that is similar to what we report in the Nfil3−/− and Ncr1-Gfp mice. This evidence concerns the gene NCR1 and pulmonary arterial hypertension.