title: High-affinity uptake and degradation of acetylated low density lipoprotein by confluent human vascular endothelial cells.
abstract: Confluent human vascular endothelial cells take up and degrade acetylated low density lipoproteins (Ac-LDL) via a high-affinity binding process, comparable to that for native LDL. The degradation of 125I-labelled Ac-LDL by endothelial cells was inhibited by the addition of unlabelled Ac-LDL but not by the addition of unlabelled LDL. Similarly, the degradation of 125I-labelled LDL could be inhibited by unlabelled LDL but not by unlabelled Ac-LDL. Unlabelled apolipoprotein E-free HDL did not compete with the degradation of either 125I-labelled LDL or Ac-LDL. Electron microscopical studies, using gold-labelled LDL and gold-labelled Ac-LDL, showed that at 4 degrees C both LDL and Ac-LDL bind to indented regions of the endothelial cell plasma membrane. At 37 degrees C both LDL and Ac-LDL were taken up and associated with lysosomes. Although morphologically identical, we conclude that the binding of LDL and Ac-LDL to human endothelial cells proceeds via 2 different high-affinity receptors. The uptake and degradation of Ac-LDL by human endothelial cells was about 25 and 15%, respectively, of that of native LDL. The uptake and degradation of either LDL or Ac-LDL did not lead to a massive increase in cellular cholesterol content.
mesh_terms: D001665:Binding Sites; D001808:Blood Vessels / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D004727:Endothelium / Q000166:cytology / Q000378:metabolism; D006046:Gold; D006801:Humans; D007457:Iodine Radioisotopes; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008854:Microscopy, Electron; D014470:Umbilical Cord / Q000098:blood supply
chemical_list: D007457:Iodine Radioisotopes; D008077:Lipoproteins, LDL; C032629:acetyl-LDL; D006046:Gold; D002784:Cholesterol