Forces involved in chylomicron binding by isolated cells of rat liver

The binding of chylomicrons by isolated liver cells has been found to decrease as temperature increases. It is greatest at the isoelectric point of the chylomicrons; although it occurs both above and below this pH, it decreases most rapidly as the pH is increased. Urea, guanidine hydrochloride, dimethylsulfoxide, dioxane, and sodium chloride at concentrations known to disrupt bonding in proteins have no effect on the removal (by centrifugation) of chylomicrons bound to liver cells. The binding is reduced by treatment of chylomicrons with phospholipase D or by addition of chylomicron "membrane" fraction, lecithin micelles, or lecithin-triglyceride-cholesterol micelles. This evidence implicates phospholipids in the binding. Treatment of liver cells with neuraminidase increases binding of chylomicrons but not the extent of lipolysis that accompanies the binding. Removal of divalent cations from the system with EDTA results in a rise both in chylomicron binding and lipolysis. It is suggested that the binding sites are accessible to the lipase that is responsible for hydrolysis.