Binding of acetylated low density lipoprotein and maleylated bovine serum albumin to the rat liver: one or two receptors?
The liver is the major organ involved in clearance of acetylated low density lipoprotein (acetyl-LDL) and maleylated serum albumin (Mal-BSA). Quantitative analysis of the hepatic uptake by sequential scintigraphy in rats shows that the hepatic uptake capacity for Mal-BSA is at least 15 times larger than for acetyl-LDL particles. A membrane-associated M approximately 250,000 daltons hepatic receptor for acetyl-LDL and Mal-BSA was 1450-fold purified from total membrane by Triton X-114 solubilization, chromatography on polyethylenimine cellulose and gel filtration. This receptor incorporated into liposomes displayed a saturable binding of [131I]Mal-BSA with a dissociation constant Kd = 15 nM and to [131I]acetyl-LDL with a dissociation constant Kd = 0.9 nM. The binding of both ligands was sensitive to poly(vinyl sulfate). The purified scavenger receptor system has a binding capacity for [131I]Mal-BSA 20 times larger than for [131I]acetyl-LDL. This is similar to the maximal removal capacity of the rat liver for both ligands in vivo. Binding studies with Mal-BSA, acetyl-LDL and anti-idiotypic receptor antibodies as competitors for [131I]Mal-BSA and [131I]acetyl-LDL binding demonstrate that [131I]Mal-BSA and [131I]acetyl-LDL compete for a common binding site. However, not all of the Mal-BSA binding sites are capable of interacting with acetyl-LDL.
D000418:Albumins / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D006801:Humans; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000097:blood / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008565:Membrane Proteins; D051381:Rats; D011971:Receptors, Immunologic / Q000378:metabolism*; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B; D012710:Serum Albumin, Bovine / Q000378:metabolism
D000418:Albumins; D008077:Lipoproteins, LDL; D008565:Membrane Proteins; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; C032629:acetyl-LDL; C049877:maleylalbumin; D012710:Serum Albumin, Bovine