Analysis of reversible lipoprotein-cell interactions.

Quantitation and characterization of freely reversible ligand-receptor interactions in adherent cell lines grown in vitro have been technically difficult to perform. We report the growth of human fibroblasts on a microcarrier bead system which obviates the limitation of cell adherence in such determinations. This system has been applied to the reversible interaction of low density lipoproteins (LDL) with the fibroblast membrane receptors. Of the 125I-LDL specifically bound to filtered cells, 52.2 +/- 9.8% was reversibly bound. This reversible LDL-cell binding occurred in less than 1 h at 37 degrees C, was specific for LDL, and occurred without significant 125I-LDL degradation. Using these techniques, it is now possible to obtain direct measurement and characterization of lipoprotein-receptor interactions in adherent cell lines of normal subjects and patients with dyslipoproteinemia.