Characteristics of chylomicron binding and lipid uptake by endothelial cells in culture.
Bovine vascular endothelial cells bind chylomicrons via a high affinity membrane receptor site. Subsequent to binding, the chylomicron apoprotein was neither internalized nor degraded by either sparse or confluent (contact-inhibited) cells. However, the adsorption of chylomicrons was associated with interiorization of chylomicron cholesteryl ester and triglyceride and the hydrolysis of these lipids to free cholesterol and unesterified fatty acids by a lysosome-dependent pathway. This pathway was active in both subconfluent and contact-inhibited cells. The chylomicron free cholesterol so produced inhibited endogeneous cholesterol synthesis measured in terms of the incorporation of [1-14C]-acetate into sterol. An excess of high density lipoprotein was 2- to 3-fold more effective in reducing both binding of chylomicrons and interiorization of chylomicron lipid than was low density lipoprotein. Chylomicron binding was not "down-regulated" by preincubation of the cells with low density lipoprotein or chylomicrons. The results are discussed in the context of cholesterol sources for contact-inhibited endothelial cells which do not interiorize low density lipoprotein cholesterol.
D000818:Animals; D001011:Aorta / Q000378:metabolism*; D001692:Biological Transport; D002417:Cattle; D002478:Cells, Cultured; D002788:Cholesterol Esters / Q000378:metabolism; D002914:Chylomicrons / Q000378:metabolism*; D004727:Endothelium / Q000378:metabolism; D005333:Fetus; D007700:Kinetics; D050356:Lipid Metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism; D008196:Lymph; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D014280:Triglycerides / Q000378:metabolism
D002788:Cholesterol Esters; D002914:Chylomicrons; D008077:Lipoproteins, LDL; D014280:Triglycerides