To evaluate the RAS activation in PAH, we assessed the angiotensin II (Ang II) and angiotensin 1-7 (Ang-(1-7) concentrations in serum and lung tissue, as well as the expressions of angiotensin-converting enzyme 2 (ACE2), angiotensin II type 1 receptor (AT1R), and angiotensin II type 2 receptor (AT2R) in the lung. This evidence concerns the gene ACE2 and pulmonary arterial hypertension.