Active hepatic capacitance responses to neural and humoral stimuli in dogs

Active changes in hepatic capacitance were studied in pump-perfused dog livers during hepatic nerve stimulation or during intrahepatic arterial infusion of histamine (0.01-1 mg/l) or epinephrine (0.05 mg/l). Hepatic nerve stimulation at 5 pulses/s (pps) reduced hepatic blood volume by 76 +/- 39 (SD) ml/kg tissue and decreased the apparent hepatic compliance 36% from a control value of 25.6 +/- 9.3 ml.kg-1.mmHg-1, with constant flow perfusion. With a constant hepatic arterial pressure, 5 pps stimulation decreased hepatic arterial flow to 16% of control; the volume expelled was 91 +/- 33 ml/kg. Epinephrine caused hepatic artery constriction, the active expulsion of 71 ml/kg of blood, and a decrease of about 30% in hepatic compliance. Histamine dramatically reduced the hepatic vascular compliance, decreased the portal venous conductance, increased hepatic arterial conductance, and caused the apparent hepatic blood volume to double. Increased hepatic venous pressure, hepatic nerve stimulation, epinephrine, and, especially, histamine caused a significant filtration of fluid from the hepatic vasculature. We conclude that significant active capacitance changes and transsinusoidal fluid filtration can be induced in the canine liver by neural and hormonal stimuli.