“…Substances like norepinephrine, substance P, thrombin, angiotensin II, (Schneider et al, 1999), endothelin (Jimenez and Rodes, 1994), prostanoids (Graupera et al, 2003) influence the contractile tone of myofibroblasts increasing portal resistance. By pharmacologically modifying the tone of myofibroblasts, a reduction in intrahepatic resistance is obtainable (Bhathal and Groszmann, 1985;Poo et al, 1992). The pivotal pathophysiological mechanism contributing to the dynamic increase in intrahepatic resistance is an endothelial dysfunction (Matei et al, 2006).…”