Sprague et al. (1996, 2001) documented impaired ATP release from the RBCs of patients with idiopathic pulmonary arterial hypertension (IPAH, then called primary pulmonary hypertension (PPH). They suggested that the elevated PVR in these patients could be in part secondary to the expected decrease in pulmonary vascular NO synthase activity that results from diminished ATP flux in the pulmonary circulation. ATP can inhibit the activity of Px1, fine-tuning the level of extracellular (exported) ATP (Qiu and Dahl, 2009). This evidence concerns the gene PANX1 and pulmonary arterial hypertension.