During PAH, there was a significant downregulation of Cav1.2 mRNA in the right ventricle, a significant downregulation of Cav1.3 mRNA in the sinus node and a significant downregulation of Cav3.1 mRNA in the right atrium and sinus node (figure 3d–f). This evidence concerns the gene CACNA1C and pulmonary arterial hypertension.