Recognition of chylomicron remnants and β-migrating very-low-density lipoproteins by the remnant receptor of parenchymal liver cells is distinct from the liver α2-macroglobulin-recognition site

• Published in: Biochemical journal 1991-11, Vol.279 (3), p.863-870
• Main Authors: VAN DIJK, M. C. M, ZIERE, G. J, LINTHORST, C, BIJSTERBOSCH, M. K, VAN BERKEL, T. J. C
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Cell receptors; Cell structures and functions; Fundamental and applied biological sciences. Psychology; Miscellaneous; Molecular and cellular biology
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2790863

The uptake in vivo of chylomicrons and beta-migrating very-low-density lipoprotein (beta-VLDL) by rat liver, which is primarily carried out by parenchymal cells, is inhibited, 5 min after injection, to respectively 35 and 8% of the control values after preinjection of lactoferrin. The decrease in the uptake of lipoproteins by the liver caused by lactoferrin is a specific inhibition of uptake by parenchymal cells. Competition studies in vitro demonstrate that chylomicron remnants and beta-VLDL compete for the same recognition site on parenchymal cells. Data obtained in vivo together with the competition studies performed in vitro indicate that chylomicron remnants and beta-VLDL interact specifically with the same remnant receptor. Hepatic uptake of 125I-labelled-alpha 2-macroglobulin in vivo, mediated equally by parenchymal and endothelial cells, is not decreased by preinjection of lactoferrin and no effect on the parenchymal-cell-mediated uptake is found. In vitro, alpha 2-macroglobulin and chylomicron remnants or beta-VLDL show no cross-competition. Culturing of parenchymal cells for 24-48 h leads to a decrease in the cell association of alpha 2-macroglobulin to 26% of the initial value, while the cell association of beta-VLDL with the remnant receptor is not influenced. It is concluded that beta-VLDL and chylomicron remnants are recognized by a specific remnant receptor on parenchymal liver cells, while uptake of alpha 2-macroglobulin by liver is carried out by a specific receptor system (presumably involving the LDL-receptor-related protein) which shows properties that are distinct from those of the remnant receptor.