Rapid hepatic clearance of the canine lipoproteins containing only the E apoprotein by a high affinity receptor. Identity with the chylomicron remnant transport process.
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.
D000818:Animals; D001053:Apolipoproteins / Q000378:metabolism*; D001692:Biological Transport; D002914:Chylomicrons / Q000378:metabolism*; D004285:Dogs; D005260:Female; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008196:Lymph / Q000378:metabolism; D010477:Perfusion; D051381:Rats; D011955:Receptors, Drug / Q000378:metabolism*
D001053:Apolipoproteins; D002914:Chylomicrons; D008075:Lipoproteins, HDL; D011955:Receptors, Drug