Hepatic binding of triglyceride-rich lipoproteins in humans

Human plasma chylomicrons (Sf greater than 200), which equals large chylomicron remnants and VLDL remnants, were obtained from a subject with hypertriglyceridaemia. These plasma chylomicrons were radioactively labelled and incubated with human liver membranes. Plasma chylomicrons bound to the membranes in lipoprotein particle form, and binding occurred to the same degree after plasma chylomicrons had been further degraded in vitro by the enzyme lipoprotein lipase. Plasma chylomicron binding to human liver membranes contained a Ca2+ dependent and a Ca2+ independent part. The Ca2+ dependent binding was saturable at 37 degrees C. A 20-fold excess of LDL only displaced 20% of plasma chylomicron binding to liver membranes, indicating binding of the two lipoproteins to different sites.