Hepatic arterial perfusion regulates portal venous flow between hepatic sinusoids and intrahepatic shunts in the normal rat liver in vitro

Intrahepatic shunts regulate portal venous pressure during periods of acute portal hypertension when the transhepatic portal resistance is momentarily increased in the normal rat liver in vivo. Hepatic arterial inflow may also increase the transhepatic portal resistance and activate intrahepatic shunts. In the present study, the transhepatic portal resistance and the activity of intra-hepatic shunts were measured in vitro and the point of confluence between the hepatic artery and portal vein in the rat determined. Livers of male Sprague-Dawley rats were single-pass, dual-perfused in vitro. Total cessation or diversion of the hepatic arterial inflow to the portal venous vasculature, whilst maintaining total hepatic perfusate flow. decreased intrasinusoidal pressure, increased transhepatic portal venous resistance and opened the portal venous intrahepatic shunts in a manner similar to intraportal injection of 15-pm diameter microspheres. Injections of the microspheres into the hepatic arterial circulation increased hepatic arterial pressure dramatically, consistent with complete occlusion of the arterial vasculature. The intrahepatic shunts are located at a pre-sinusoidal level because no increases were detected in hepatic arterial pressure following intraportal injection of microspheres. The hepatic arterial vasculature, unlike the portal supply, does not possess a collateral shunt circulation and coalesces with the portal vein at an intrasinusoidal location.