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Hepatic uptake of chylomicron remnants in WHHL rabbits: a mechanism genetically distinct from the low density lipoprotein receptor. 1982

T Kita, and J L Goldstein, and M S Brown, and Y Watanabe, and C A Hornick, and R J Havel

Homozygous Watanabe hereditary hyperlipidemic (WHHL) rabbits have a near-complete deficiency of low density lipoprotein (LDL) receptors in liver and other tissues. As a result, these rabbits clear LDL from plasma at an abnormally slow rate. In the current studies we show that WHHL rabbits clear chylomicrons from plasma at a normal rate. Chylomicrons are cleared by a two-step process: (i) hydrolysis of triglycerides in extrahepatic tissues to yield cholesteryl ester-rich remnant particles and (ii) rapid uptake of the remnants by liver. Normal and WHHL rabbits were given intravenous injections of rat chylomicrons labeled either in the lipid portion with [3H]cholesterol and [14C]palmitate or in the protein portion with [125]iodine. All radiolabeled components were removed from plasma at comparable rates in normal and WHHL rabbits. Comparable amounts of radioactivity accumulated in livers of animals from both genotypes. In vitro assays showed that liver membranes from WHHL rabbits were markedly deficient in the binding of 125I-labeled chylomicron remnants as well as 125I-labeled LDL, implying that chylomicron remnants can bind to the hepatic LDL receptor. We conclude that the rabbit liver normally has at least two genetically distinct lipoprotein uptake mechanisms, both of which recognize chylomicron remnants: (i) the LDL receptor and (ii) a specific chylomicron remnant uptake mechanism that is not measured adequately by current in vitro membrane binding assays. WHHL rabbits possess a normal chylomicron remnant uptake mechanism that allows them to clear chylomicrons from plasma at a rapid rate despite their genetic deficiency of LDL receptors.

UI MeSH Term Description Entries
D008099 Liver A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances. Livers
D008657 Metabolic Clearance Rate Volume of biological fluid completely cleared of drug metabolites as measured in unit time. Elimination occurs as a result of metabolic processes in the kidney, liver, saliva, sweat, intestine, heart, brain, or other site. Total Body Clearance Rate,Clearance Rate, Metabolic,Clearance Rates, Metabolic,Metabolic Clearance Rates,Rate, Metabolic Clearance,Rates, Metabolic Clearance
D011817 Rabbits A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes. Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
D011956 Receptors, Cell Surface Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands. Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D011973 Receptors, LDL Receptors on the plasma membrane of nonhepatic cells that specifically bind LDL. The receptors are localized in specialized regions called coated pits. Hypercholesteremia is caused by an allelic genetic defect of three types: 1, receptors do not bind to LDL; 2, there is reduced binding of LDL; and 3, there is normal binding but no internalization of LDL. In consequence, entry of cholesterol esters into the cell is impaired and the intracellular feedback by cholesterol on 3-hydroxy-3-methylglutaryl CoA reductase is lacking. LDL Receptors,Lipoprotein LDL Receptors,Receptors, Low Density Lipoprotein,LDL Receptor,LDL Receptors, Lipoprotein,Low Density Lipoprotein Receptor,Low Density Lipoprotein Receptors,Receptors, Lipoprotein, LDL,Receptor, LDL,Receptors, Lipoprotein LDL
D002914 Chylomicrons A class of lipoproteins that carry dietary CHOLESTEROL and TRIGLYCERIDES from the SMALL INTESTINE to the tissues. Their density (0.93-1.006 g/ml) is the same as that of VERY-LOW-DENSITY LIPOPROTEINS. Chylomicron
D004195 Disease Models, Animal Naturally-occurring or experimentally-induced animal diseases with pathological processes analogous to human diseases. Animal Disease Model,Animal Disease Models,Disease Model, Animal
D006938 Hyperlipoproteinemia Type II A group of familial disorders characterized by elevated circulating cholesterol contained in either LOW-DENSITY LIPOPROTEINS alone or also in VERY-LOW-DENSITY LIPOPROTEINS (pre-beta lipoproteins). Hyperbetalipoproteinemia,Hypercholesterolemia, Essential,Hypercholesterolemia, Familial,Apolipoprotein B-100, Familial Defective,Apolipoprotein B-100, Familial Ligand-Defective,Familial Combined Hyperlipoproteinemia,Hyper-Low Density Lipoproteinemia,Hyper-Low-Density-Lipoproteinemia,Hyper-beta-Lipoproteinemia,Hypercholesterolemia, Autosomal Dominant,Hypercholesterolemia, Autosomal Dominant, Type B,Hypercholesterolemic Xanthomatosis, Familial,Hyperlipoproteinemia Type 2,Hyperlipoproteinemia Type IIa,Hyperlipoproteinemia Type IIb,Hyperlipoproteinemia, Type II,Hyperlipoproteinemia, Type IIa,LDL Receptor Disorder,Apolipoprotein B 100, Familial Defective,Apolipoprotein B 100, Familial Ligand Defective,Autosomal Dominant Hypercholesterolemia,Autosomal Dominant Hypercholesterolemias,Combined Hyperlipoproteinemia, Familial,Combined Hyperlipoproteinemias, Familial,Density Lipoproteinemia, Hyper-Low,Density Lipoproteinemias, Hyper-Low,Disorder, LDL Receptor,Disorders, LDL Receptor,Dominant Hypercholesterolemia, Autosomal,Dominant Hypercholesterolemias, Autosomal,Essential Hypercholesterolemia,Essential Hypercholesterolemias,Familial Combined Hyperlipoproteinemias,Familial Hypercholesterolemia,Familial Hypercholesterolemias,Familial Hypercholesterolemic Xanthomatoses,Familial Hypercholesterolemic Xanthomatosis,Hyper Low Density Lipoproteinemia,Hyper beta Lipoproteinemia,Hyper-Low Density Lipoproteinemias,Hyper-Low-Density-Lipoproteinemias,Hyper-beta-Lipoproteinemias,Hyperbetalipoproteinemias,Hypercholesterolemias, Autosomal Dominant,Hypercholesterolemias, Essential,Hypercholesterolemias, Familial,Hypercholesterolemic Xanthomatoses, Familial,Hyperlipoproteinemia Type 2s,Hyperlipoproteinemia Type IIas,Hyperlipoproteinemia Type IIbs,Hyperlipoproteinemia Type IIs,Hyperlipoproteinemia, Familial Combined,Hyperlipoproteinemias, Familial Combined,Hyperlipoproteinemias, Type II,Hyperlipoproteinemias, Type IIa,LDL Receptor Disorders,Lipoproteinemia, Hyper-Low Density,Lipoproteinemias, Hyper-Low Density,Receptor Disorder, LDL,Receptor Disorders, LDL,Type 2, Hyperlipoproteinemia,Type II Hyperlipoproteinemia,Type II Hyperlipoproteinemias,Type IIa Hyperlipoproteinemia,Type IIa Hyperlipoproteinemias,Xanthomatoses, Familial Hypercholesterolemic,Xanthomatosis, Familial Hypercholesterolemic
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001053 Apolipoproteins Protein components on the surface of LIPOPROTEINS. They form a layer surrounding the hydrophobic lipid core. There are several classes of apolipoproteins with each playing a different role in lipid transport and LIPID METABOLISM. These proteins are synthesized mainly in the LIVER and the INTESTINES. Apolipoprotein

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