title: Different expression of modified low density lipoprotein receptors in rabbit peritoneal macrophages and Kupffer cells.
abstract: We have previously reported that mouse peritoneal macrophages have three types of modified low density lipoprotein (LDL) receptors. One is specific for acetylated LDL (Ac-LDL), the second is for oxidized LDL (Ox-LDL), and the third recognizes both (Arai, H. et al. (1989) Biochem. Biophys. Res. Commun. 159, 1375-1382). In the current study, the characteristics of modified LDL receptors in rabbit peritoneal macrophages and Kupffer cells from rabbits were investigated. Cross-competition studies of the degradation assay between Ox-LDL and Ac-LDL in rabbit peritoneal macrophages showed that the degradation of 125I-labeled Ox-LDL was almost completely inhibited by an excess amount of unlabeled Ac-LDL. On the other hand, an excess amount of unlabeled Ox-LDL suppressed 125I-labeled Ac-LDL degradation only partially. In contrast, in Kupffer cells an excess amount of unlabeled Ox-LDL inhibited the degradation of 125I-labeled Ac-LDL almost completely, whereas the degradation of 125I-labeled Ox-LDL was inhibited only partially by Ac-LDL. Scatchard analysis of binding assay showed that rabbit peritoneal macrophages have a single class of receptor for Ox-LDL, which binds maximally 0.31 microgram/mg cellular protein (Bmax) with an apparent dissociation constant (Kd) of 19.3 micrograms/ml, and two classes of receptors for Ac-LDL; one with high affinity (Bmax 0.025 microgram/mg cellular protein, Kd 0.040 micrograms/ml) and the other with low affinity (Bmax 0.08 microgram/mg cellular protein, Kd 11.31 micrograms/ml). On the other hand, Kupffer cells have two classes for Ox-LDL; one is a high affinity receptor (Bmax 0.53 microgram/mg cellular protein, Kd 0.99 microgram/ml) and the other is a low affinity receptor (Bmax 3.71 micrograms/mg cellular protein, Kd 16.2 micrograms/ml) and a single class for Ac-LDL (Bmax 0.60 microgram/mg cellular protein, Kd 7.24 micrograms/ml). These results indicate that rabbit peritoneal macrophages have two kinds of modified LDL receptors; one is specific for Ac-LDL, and the other recognizes both Ox-LDL and Ac-LDL.
authors.affiliation: Department of Geriatric Medicine, Faculty of Medicine, Kyoto University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ueda
authors.forename: H
authors.initials: H
authors.lastname: Arai
authors.forename: A
authors.initials: A
authors.lastname: Kawashima
authors.forename: Y
authors.initials: Y
authors.lastname: Nagano
authors.forename: M
authors.initials: M
authors.lastname: Cho
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
authors.forename: T
authors.initials: T
authors.lastname: Kita
mesh_terms: D000107:Acetylation; D000818:Animals; D002478:Cells, Cultured; D007728:Kupffer Cells / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D011817:Rabbits; D011973:Receptors, LDL / Q000378:metabolism*
chemical_list: D008077:Lipoproteins, LDL; D011973:Receptors, LDL