High affinity binding of chylomicron remnants to rat liver plasma membranes

The binding of chylomicron remnants rat liver plasma membranes was studied. Liver membranes bound up to 8 times more remnants than they bound chylomicrons. The remnant particle appeared to bind to the membrane as a unit. Remnant binding was greatest to liver plasma membrane; only one third as much binding was observed with whole liver homogenate, and virtually no binding occurred to erythrocyte membranes or glass. Binding was saturable and had kinetics compatible with the existence of a high affinity site. Half-maximal binding occurred at 27 micron. Competitive binding studies revealed no competition with albumin, a triglyceride dispersion, cholesterol/lecithin vesicles, very low density lipoprotein, or low density lipoprotein. Some displacement of remnant binding was observed with chylomicrons and high density lipoprotein. Binding was decreased by treatment of the membranes with trypsin or the presence of heparin in the incubation medium. These studies suggest that there is a high affinity receptor for the chylomicron remnant on the surface of the hepatocyte.