CHANGES IN RECEPTOR-MEDIATED ENDOCYTOSIS IN LIVER SINUSOIDAL CELLS AFTER PARTIAL-HEPATECTOMY IN THE RAT

Liver sinusoidal cells play an important role in host defense by clear ing particulate matter and macromolecules from the circulation. In thi s study, receptor-mediated endocytosis in sinusoidal cells was examine d in two-thirds hepatectomized rats using I-125-labeled formaldehyde-t reated bovine serum albumin (fBSA) as an endocytable macromolecule. Th e liver-weight to body-weight ratio in hepatectomized rats returned to the control value 10 days after hepatectomy. The endocytotic index fo r fBSA in sinusoidal cells decreased significantly to 0.0210+/-0.0017 (controls, 0.0598+/-0.0019) on the first day, then returned to the con trol level at 5 days (0.0554+/-0.0030). The changes in hepatic uptake for fBSA showed a similar time course of the endocytotic index. A tran sient increase in the uptake of fBSA per unit weight of liver of 22-39 % above control occurred 2 to 3 days after hepatectomy. In contrast to fBSA, the endocytotic index in hepatocytes evaluated with I-125-label ed asialofetuin reached the minimum level on the second day, and then recovered to the control level 10 days after hepatectomy. These result s suggest that endocytosis of fBSA by sinusoidal cells decreases after hepatectomy and rapidly recovers to normal before the completion of l iver regeneration, whereas endocytosis of asialofetuin by hepatocytes decreases following hepatic resection and returns to normal when regen eration is substantially complete.