Functional abnormalities of sinusoidal endothelial cells in rats with acute liver rejection

The purpose of this study was to determine the changes of hepatic sinusoidal endothelial cell (SEC) function in acute liver rejection with respect to receptor-mediated endocytosis. Orthotopic rat liver transplantation was performed in Lewis rats grafted with DA livers and in Lewis rats grafted with Lewis livers as rejectors and controls, respectively. Animals were killed at 1, 3, 5, 7, and 10 days after the operation. Fc receptors (FcRs) were histochemically stained on frozen liver sections by applying peroxidase-antiperoxidase IgG complex as a ligand, and the FcR activity, i.e., capacity of binding the ligands represented by the FcR staining intensity, was semiquantitatively analyzed as an indicator of SEC function. The serum level of hyaluronic acid, which is specifically cleared from the circulation by receptor-mediated SEC endocytosis, was also assayed, along with the total serum bilirubin. Three days after the operation, the SECs of rejectors showed a significantly weaker FcR staining intensity of about half the value of that seen in the controls (P < 0.05), and staining disappeared after 5 days (P < 0.01). The decrease of FcR staining intensity, i.e., FcR activity, showed a correlation with elevation of the serum hyaluronic acid level (r = -0.77; P < 0.001). Histological evidence of endothelialitis and a significant elevation of total serum bilirubin (P < 0.01) were also present at 3 and 5 days, respectively. These results suggest that impairment of the endocytic function of SECs occurs at an earlier phase of acute liver rejection when compared with development of abnormalities of traditional indicators. Determination of receptor-mediated SEC endocytic functions may thus provide useful information for the early diagnosis of acute rejection.