ADRA1B and pulmonary arterial hypertension: As expected, the expression of three alpha 1-adrenergic receptor genes, Adra1a, Adra1b, and Adra1d, was significantly decreased in PAH mice as compared to that in pregnant WT mice (Fig. 1, F–H), but not beta-adrenergic receptor genes (Fig. S1, A–C), indicating that the alpha 1-adrenergic receptor subtype genes are selectively downregulated.