Hepatic arterial and portal venous pressure-flow relationships in isolated, perfused liver

Blood pressure responses to alteration in blood flow were studied in the completely isolated, excised liver of the calf during perfusion of the hepatic artery or portal vein. The pressure-flow curves in both of the afferent vessels of the liver are curvilinear, with concavity toward the pressure axis. Resistance increases progressively with increases in perfusion rate; resistance increases are proportionately of greater magnitude than the increases in blood flow demonstrating autoregulation in both hepatic arterial and portal venous systems. The autoregulatory nature of pressure-flow responses is not affected by prolonged perfusion or marked acidosis.