Endocytosis of Acetylated Low-Density Lipoprotein, Endothelial Cell-Modified Low-Density Lipoprotein, and Formaldehyde-Treated Serum Albumin by Rat Liver Endothelial Cells Evidence of Uptake via a Common Receptor

Abstract

Formaldehyde-treated serum albumin (FSA) and acetylated low-density lipoprotein (Ac-LDL) are taken up in vivo and in vitro by the sinusoidal endothelial cells of the liver. It is not known whether both these ligands are removed by the scavenger receptor. We have studied the effect of increasing concentrations of unlabeled FSA, Ac-LDL, and endothelial cell-modified LDL (Ec-LDL) on the endocytosis of trace amounts of these ligands labeled with ¹²⁵I. Uptake of ¹²⁵I-Ac-LDL and ¹²⁵Ec-LDL was strongly inhibited by FSA. Likewise, Ac-LDL and Ec-LDL reduced the uptake of ¹²⁵I-FSA effectively. Our data indicate that these modified LDLs and FSA are bound to and internalized via the same receptor on liver endothelial cells.

Key Words:

• Formaldehyde-treated serum albumin
• liver endothelial cells
• low-density lipoprotein
• modified
• scavenger receptor