When the level of intracellular MRP4 is decreasing or inhibited, the significant reduction of the stability of SMC results in the decrease of proliferation cells and increase of apoptosis, which may be involved in the pathogenesis of idiopathic pulmonary arterial hypertension (IPAH) and coronary heart disease (CHD) [16, 17]. This evidence concerns the gene ABCC4 and idiopathic pulmonary arterial hypertension.