When the liver is damaged, endothelial cell ET-1 expression is increased and NO production is decreased; the balance between the contraction and vasodilation of hepatic sinusoid and vessels is disrupted, and ET-1 contraction dominates, causing vasoconstriction, hepatic sinusoid stasis, increased intrahepatic vascular resistance, upregulated leukocyte–endothelial cell interaction, and portal hypertension (Feng et al. 2009; Rosado et al. 2012). The gene discussed is EDN1; the disease is portal hypertension.