Endocytic mechanisms for uptake and metabolism of chylomicron remnants in the liver.

Removal of small chylomicron remnants by perfused rat livers closely correlates with the LDL-receptor mRNA modulated by various interventions. In contrast, removal of remnants of large chylomicrons is not appreciably influenced by the activity of the hepatic LDL-receptor. Their primary removal depends on a heparinase-sensitive binding site. Transient and stable transfection of the cDNAs of the two subunits of the human asialoglycoprotein receptor markedly increased the binding capacity for chylomicron remnants suggesting the asialoglycoprotein receptor to be an alternative mechanism for remnant removal. Some species can edit apolipoprotein B-100 mRNA and thus secret apolipoprotein B-48 containing lipoproteins of hepatic origin. Generally these animals have lower cholesterol levels and a more favorable lipoprotein profile.