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Turnover and uptake by organs of radioactive serum high-density lipoprotein cholesteryl esters and phospholipids in the rat in vivo. 1981

F M Van't Hooft, and T Van Gent, and A Van Tol

The serum decay of rat serum high-density lipoprotein (HD lipoprotein), labelled biosynthetically with (32)P in the phospholipid or with (3)H in the cholesteryl ester moiety, was measured in rats after partial hepatectomy or sham operation. The serum decay of (3)H-labelled HD lipoprotein cholesteryl esters was biexponential. In sham-operated rats the t((1/2)) values for the rapid phase and the slow phase were 0.2+/-0.1h and 4.2+/-0.4h (means+/-s.e.m.) respectively. After removal of two-thirds of the liver the t((1/2)) value of the rapid phase did not change (0.1+/-0.1h), whereas the t((1/2)) value of the slow phase increased to 5.7+/-0.8h. Partial hepatectomy hardly changed extrahepatic tissue radioactivities, whereas the percentage of the injected dose recovered in the liver 6h after injection decreased from 34.0+/-1.9% before to 13.5+/-1.6% after partial hepatectomy. The (32)P-labelled HD lipoprotein phospholipids showed a rapid monoexponential decay from serum with t((1/2)) values of 0.71+/-0.3h and 1.48+/-0.11h after sham operation or partial hepatectomy respectively. The tissue (32)P radioactivities in the shamoperated rats, measured 1h after injection, were 46.0+/-1.7% (liver), 1.7+/-0.3% (adipose tissue), 3.7+/-1.2% (skeletal muscle) and 3.0+/-0.0% (erythrocytes) of the injected dose. Only the value for liver was affected by partial hepatectomy and decreased to 16.7+/-3.8%. In a previous publication [Van Tol, Van Gent, Van't Hooft & Vlaspolder (1978) Atherosclerosis29, 439-448] we showed in a highly comparable experimental setting that the turnover rates of HD apolipoproteins A and C in vivo are not influenced by removal of two-thirds of the liver. From the present study it is clear that the removal rates of radioactive HD lipoprotein cholesteryl esters and HD lipoprotein phospholipids from serum in vivo are decreased by partial hepatectomy. The results indicate the possibility of partly separate metabolic pathways of HD apolipoproteins A and C, HD lipoprotein cholesteryl esters and HD lipoprotein phospholipids. The phospholipids and cholesteryl esters of HD lipoprotein are metabolized predominantly by the liver. Possible mechanisms for the hepatic uptake and metabolism of HD lipoprotein cholesteryl (esters) and phospholipids are discussed.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008075 Lipoproteins, HDL A class of lipoproteins of small size (4-13 nm) and dense (greater than 1.063 g/ml) particles. HDL lipoproteins, synthesized in the liver without a lipid core, accumulate cholesterol esters from peripheral tissues and transport them to the liver for re-utilization or elimination from the body (the reverse cholesterol transport). Their major protein component is APOLIPOPROTEIN A-I. HDL also shuttle APOLIPOPROTEINS C and APOLIPOPROTEINS E to and from triglyceride-rich lipoproteins during their catabolism. HDL plasma level has been inversely correlated with the risk of cardiovascular diseases. High Density Lipoprotein,High-Density Lipoprotein,High-Density Lipoproteins,alpha-Lipoprotein,alpha-Lipoproteins,Heavy Lipoproteins,alpha-1 Lipoprotein,Density Lipoprotein, High,HDL Lipoproteins,High Density Lipoproteins,Lipoprotein, High Density,Lipoprotein, High-Density,Lipoproteins, Heavy,Lipoproteins, High-Density,alpha Lipoprotein,alpha Lipoproteins
D008076 Cholesterol, HDL Cholesterol which is contained in or bound to high-density lipoproteins (HDL), including CHOLESTEROL ESTERS and free cholesterol. High Density Lipoprotein Cholesterol,Cholesterol, HDL2,Cholesterol, HDL3,HDL Cholesterol,HDL(2) Cholesterol,HDL(3) Cholesterol,HDL2 Cholesterol,HDL3 Cholesterol,alpha-Lipoprotein Cholesterol,Cholesterol, alpha-Lipoprotein,alpha Lipoprotein Cholesterol
D008297 Male Males
D010743 Phospholipids Lipids containing one or more phosphate groups, particularly those derived from either glycerol (phosphoglycerides see GLYCEROPHOSPHOLIPIDS) or sphingosine (SPHINGOLIPIDS). They are polar lipids that are of great importance for the structure and function of cell membranes and are the most abundant of membrane lipids, although not stored in large amounts in the system. Phosphatides,Phospholipid
D010761 Phosphorus Radioisotopes Unstable isotopes of phosphorus that decay or disintegrate emitting radiation. P atoms with atomic weights 28-34 except 31 are radioactive phosphorus isotopes. Radioisotopes, Phosphorus
D002784 Cholesterol The principal sterol of all higher animals, distributed in body tissues, especially the brain and spinal cord, and in animal fats and oils. Epicholesterol
D002788 Cholesterol Esters Fatty acid esters of cholesterol which constitute about two-thirds of the cholesterol in the plasma. The accumulation of cholesterol esters in the arterial intima is a characteristic feature of atherosclerosis. Cholesterol Ester,Cholesteryl Ester,Cholesteryl Esters,Ester, Cholesterol,Ester, Cholesteryl,Esters, Cholesterol,Esters, Cholesteryl
D006207 Half-Life The time it takes for a substance (drug, radioactive nuclide, or other) to lose half of its pharmacologic, physiologic, or radiologic activity. Halflife,Half Life,Half-Lifes,Halflifes
D006498 Hepatectomy Excision of all or part of the liver. (Dorland, 28th ed) Hepatectomies

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