EFFECT OF PLATELET-ACTIVATING-FACTOR ON HEPATIC CAPILLARY-PRESSURE INISOLATED DOG LIVER

We determined the effects of platelet-activating factor (PAF), a poten t vasoactive autacoid phospholipid, on the capillary pressure and live r weight (Wt) in isolated canine livers perfused with blood bivascular ly via the portal vein and hepatic artery. PAF (0.01-33 mu g) administ ered intraportally produced dose-dependent increases in the hepatic ca pillary pressure, as assessed by triple vascular occlusion pressure (P to), and Wt. An intraportal injection of 10 mu g PAF produced increase s in Pto by 10 mmHg and Wt by 35 g/100 g liver weight. This hepatic va soconstriction was attributed to a threefold increase in the portal ve in resistance and a fourfold increase in the hepatic vein resistance. The hepatic arterial resistance was not changed when PAF was arteriall y or intraportally injected. In conclusion, in isolated perfused dog l ivers, PAF increases the hepatic capillary pressure and liver weight d ue to contraction of both the portal vein and hepatic vein, but not th e hepatic artery.