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  • Title: Different expression of modified low density lipoprotein receptors in rabbit peritoneal macrophages and Kupffer cells.
    Author: Ueda Y, Arai H, Kawashima A, Nagano Y, Cho M, Tanaka M, Kita T.
    Journal: Atherosclerosis; 1993 Jun; 101(1):25-35. PubMed ID: 8216500.
    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.
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