Effects of local thrombinaemia and endotoxinaemia on hepatic circulation in the anaesthetized dog.

The acute response of the hepatic circulation to thrombinaemia and endotoxinaemia were investigated in the anaesthetized dog. Small amounts of thrombin were infused into the hepatic artery and portal vein. The effects of thrombin were compared to those of minor amounts of portally infused endotoxin. Portal pressure increased significantly following portal infusion of thrombin and endotoxin. Both substances decreased the blood flow markedly in the hepatic artery, while that in the superior mesenteric artery and portal vein decreased only slightly. Heparin and polyphlorethin phosphate (PPP) abolished all effects of thrombin. Bradykinin infused simultaneously inhibited only the effect on the hepatic artery. Vasoactive intestinal peptide, which has the same vasodilatory effect in the liver, did not. It is believed that thrombin and perhaps endotoxin exert a vasoconstrictive effect mediated by products released from platelets.