ITSN1 and pulmonary arterial hypertension: The functional effects of ITSN deficiency and EHITSN expression on lung microvascular permeability were also assessed in the lungs of the MCT-rat model of PAH, by 10 min perfusion of 10 mg/ml DNP-BSA through lung microvasculature and quantifying by ELISA the amounts of DNP-BSA tracer transported to lung interstitial space.