Rapid hepatic clearance of the canine lipoproteins containing only the E apoprotein by a high affinity receptor. Identity with the chylomicron remnant transport process

• Published in: The Journal of biological chemistry Vol. 255; no. 5; pp. 1804 - 1807
• Main Authors: Sherrill, B C, Innerarity, T L, Mahley, R W
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 10.03.1980
• Subjects: Animals; Apolipoproteins - metabolism; Biological Transport; Chylomicrons - metabolism; Dogs; Female; Kinetics; Lipoproteins, HDL - metabolism; Liver - metabolism; Lymph - metabolism; Perfusion; Rats; Receptors, Drug - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)85951-3

The canine lipoproteins containing only the E apoprotein (apo-E HDLc), when perfused through a rat liver, display high affinity, receptor-mediated uptake, and saturation kinetics. These data indicate that the hepatic uptake of apo-E HDLc proceeds via a finite number of binding sites. The kinetic values determined for apo-E HDLc binding and uptake during a single-pass perfusion through a rate liver are: Km = 4.99 micrograms of protein . ml-1 and Vmax = 6.42 microgram of protein . g-1 . min-1. On a molar basis, the hepatic extraction of apo-E HDLc is almost equivalent to the high hepatic extraction of a class of lipoproteins that is most avidly removed from systemic circulation--the rat chylomicron remnants. Competition experiments between apo-E HDLc and rat chylomicron remnants indicate that the hepatic uptake mechanism for the two macromolecules is identical. Given that the recognition of apo-E HDLc is mediated by the E apoprotein and that the kinetic uptake properties of chylomicron remnants and apo-E HDLc are almost identical, it is probable that the E apoprotein is the major determinant responsible for hepatic chylomicron remnant recognition.