Ueda Y, Arai H, Kawashima A, Nagano Y, Cho M, Tanaka M, Kita T
Department of Geriatric Medicine, Faculty of Medicine, Kyoto University, Japan.
Atherosclerosis. 1993 Jun;101(1):25-35. doi: 10.1016/0021-9150(93)90098-f.
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.
我们之前报道过，小鼠腹腔巨噬细胞有三种类型的修饰低密度脂蛋白（LDL）受体。一种对乙酰化LDL（Ac-LDL）具有特异性，第二种对氧化LDL（Ox-LDL）具有特异性，第三种则能识别两者（新井，H.等人（1989年）《生物化学与生物物理学研究通讯》159，1375 - 1382）。在当前研究中，对兔腹腔巨噬细胞和兔库普弗细胞中修饰LDL受体的特性进行了研究。兔腹腔巨噬细胞中Ox-LDL与Ac-LDL降解试验的交叉竞争研究表明，过量的未标记Ac-LDL几乎完全抑制了125I标记的Ox-LDL的降解。另一方面，过量的未标记Ox-LDL仅部分抑制了125I标记的Ac-LDL的降解。相比之下，在库普弗细胞中，过量的未标记Ox-LDL几乎完全抑制了125I标记的Ac-LDL的降解，而125I标记的Ox-LDL的降解仅被Ac-LDL部分抑制。结合试验的Scatchard分析表明，兔腹腔巨噬细胞对Ox-LDL有一类单一受体，其最大结合量为0.31微克/毫克细胞蛋白（Bmax），表观解离常数（Kd）为19.3微克/毫升，对Ac-LDL有两类受体；一类具有高亲和力（Bmax 0.025微克/毫克细胞蛋白，Kd 0.040微克/毫升），另一类具有低亲和力（Bmax 0.08微克/毫克细胞蛋白，Kd 11.31微克/毫升）。另一方面，库普弗细胞对Ox-LDL有两类受体；一类是高亲和力受体（Bmax 0.53微克/毫克细胞蛋白，Kd 0.99微克/毫升），另一类是低亲和力受体（Bmax 3.71微克/毫克细胞蛋白，Kd 16.2微克/毫升），对Ac-LDL有一类单一受体（Bmax 0.60微克/毫克细胞蛋白，Kd 7.24微克/毫升）。这些结果表明，兔腹腔巨噬细胞有两种修饰LDL受体；一种对Ac-LDL具有特异性，另一种能识别Ox-LDL和Ac-LDL两者。
