Immunoenzyme assessment of human apoB-lipoprotein binding to immobilized receptor of low density lipoproteins. 2. Binding of isolated lipoproteins.

The receptor of low density lipoproteins (LDL-receptor) from bovine adrenal cortex membranes was immobilized in standard 96-well polystyrene plates using monoclonal V5-antibodies to the LDL-receptor. The binding of the immobilized LDL-receptor with human low density lipoproteins (LDL) and very low density lipoproteins (VLDL) was determined using peroxidase-labelled antibodies to human apoB. The value of Kd for the interaction of LDL with the immobilized LDL-receptor for 40 samples of LDL was found to be from 5 to 20 micrograms apoB per ml. The immobilized LDL-receptor failed to bind LDL modified by acetylation or malonic dialdehyde, while the binding of non-modified LDL to the immobilized LDL-receptor was inhibited in the presence of EDTA, which is known to be specific for the interaction of LDL with the LDL-receptor. Unlike LDL, VLDL were more variable in the binding to the LDL-receptor. The value of Kd for the interaction of VLDL with the LDL-receptor for 40 samples of VLDL was found to be from 0.5 to 10 micrograms apoB per ml. Thus, the described method is suggested to study the interaction of apoB-containing lipoproteins with the LDL-receptor.