大鼠肝细胞膜高密度脂蛋白受体的研究

HIGH DENSITY LIPOPROTEIN RECEPTOR ON RAT LIVER PLASMA MEMBRANES

以~125碘标记不含apoE的人HDL_3为配体,采用简便的聚乙二醇沉淀分离法,建立了纯化的大鼠肝细胞膜HDL受体分析法,并对膜HDL受体的性质进行了研究。

A simple radioassay of HDL-binding sites on purified rat liver plasma membranes with polyethyleneglycol (PEG) precipitation separation of B/F was developed, ^(125)I-labeled apoE-deficient human HDL_3 was prepared as the ligand. 12.5％ of the final PEG concentration could effeciently sediment the ^(125)I-labeled HDL_3-membrane complex, and more than 94％ of the total binding was specific (non-specific binding was determined at the presence of 25fold excess HDL_3). A saturable and high affinity HDL-binding site on liver membranes with kd 14.5±0.86μg/ml (16.6 × 10^(-8)mol/L) and B_(max), 15.6±6.8μg/mg membrane protein was found. The B_(max) of this HDL-binding appeared to increase as the reactiontemperature rose. The binding activity of this HDL receptor, was not inhibited by 0—30 m mol/L EDTA and not activated by 0—5.0mmol/L Ca^(2+), as well as insensitive to trypsin. Human HDL_3 and rat HDL, but not human VLDL, LDL and albumin, could effectively inhibit the ^(125)Ilabeled HDL_3 binding to the liver membranes. The ^(125)I-labeled HDL_3 binding activity (μg/mg membrane protein) increased with the increasing of the liver membrane purity. These results suggest that there was a saturable and highly specific HDL-receptor on liver plasma membranes, and its biologic properties are different from LDL-and apoE-receptors.