Vena cava perfusion in situ: a tool for uptake studies.

While studying the uptake of trypsin and thrombin by the perfused rat liver, we verified that these proteins are internalized neither by hepatocytes nor Kupffer cells. These results raised the possibility that the enzymes might be binding to endothelial cells, either hepatic or vascular. In order to find out if the binding of enzymes to endothelial surface is a liver cell-specific phenomenon, we devised a system to perfuse the rat inferior cava vein in situ. After exsanguination, the vein was perfused with the recirculation of 30 mL of Krebs/BSA solution propellered by a pulsatile flow pump (10 mL/min). The liver was not exsanguinated, but to assure that the organ was indeed excluded from the circuit during the experiment at the end of the perfusion time we added China ink in the perfusion fluid. We verified that trypsin is extracted from the perfusion fluid by the vena cava as efficiently as by the liver, suggesting that the most of the infused trypsin is removed mainly by vascular endothelial cells when the liver perfusion model is used. On the other hand, thrombin is removed mainly by the liver cells since the uptake by the vena cava was insignificant.