Evidence that the RhoA/ROK pathway contributes to the vasoconstrictor component of pulmonary hypertension is demonstrated by effects of ROK inhibitors to acutely reduce pulmonary arterial pressure in both chronically hypoxia rats and in the hypoxia/SU5416 rat model of angioproliferative PAH [32, 33, 35, 36]. This evidence concerns the gene RHOA and pulmonary arterial hypertension.