Local control of hepatic arterial and portal venous flow in the dog

Abstract

Hemodynamic studies were made in over 100 experiments on the denervated, autoperfused, dog liver in situ. Electromagnetic flowmeters were used. Data are given on pressure-flow relationships in both vascular circuits, with and without simultaneous flow in the opposite system. Autoregulation of hepatic artery flow was seen in 60% of the artery pressure-flow experiments with intact portal flow. A 67% pressure reduction resulted in a 28% resistance decrease. Shunting of portal inflow decreased the incidence of autoregulation. Observations were made on reciprocal relationships between the 2 vascular beds. Reduction of portal inflow by 67% resulted in an increased artery inflow and a 29% decrease in artery resistance. Reduction in artery pressure resulted in decreased portal pressure and resistance, although portal inflow showed no change. Elevation of hepatic venous pressure was accompanied by increased arterial resistance and decreased portal resistance. A unified hypothesis is presented explaining arterial autoregulation, arterial resistance responses to hepatic venous pressure, and flow reciprocity, based on a common mechanism: a myogenic response of arterial resistance vessels. Portal venous autoregulation was not seen.