HIF1A and fetal growth restriction: In a study conducted on newborn rats with intrauterine growth retardation (IUGR), maternal nutritional restriction and hypoxic conditions resulted in a significant increase in histone acetylation levels within the ET-1 gene promoter of pulmonary vascular endothelial cells.226 This increase facilitated the binding of HIF-1α to the promoter, subsequently enhancing the expression of ET-1 in ECs (Fig. 3a).