The levels of apolipoprotein-E in hypercholesteroiemic rat serum

1978 ◽  
Vol 56 (3) ◽  
pp. 161-166 ◽  
Author(s):  
Laurence Wong ◽  
David Rubinstein
Keyword(s):  
Golgi Apparatus ◽  
Apolipoprotein E ◽  
Fold Increase ◽  
Low Density Lipoproteins ◽  
Low Density ◽  
Very Low Density Lipoproteins ◽  
Rat Serum ◽  
Apo E ◽  
Control Serum ◽  
Lipoprotein Complex

The levels of apolipoprotein-E (apo-E) in serum and isolated lipoproteins from diet-induced hypercholesterolemic, and to some extent, hypertriglycerdemic rats were measured by electroimmunoassay. The hypocholesterolemia was accompanied by a mild hypertriglyceridemia. The apo-E was increased by 60% in the hypercholesterolemic serum with a 5- and 50-fold increase in very low density lipoproteins (VLDL) and low density lipoproteins (LDL) respectively. However, the proportion of apo-E in nascent VLDL isolated from the hepatic Golgi apparatus of hypercholesterolemic rats was significantly decreased. In control serum, 40–50% of the apo-E is found in the density >1.21 g/ml fraction, although this is at least partially due to ultracentrifugation. The aproprotein is absent from the density >1.21 g/ml fraction from hypercholesterolemic serum, suggesting that it is bound more firmly to the lipoprotein complex. It is concluded that the large increases in apo-E in the VLDL and LDL density ranges of serum from hypercholesterolemic rats may in part be accounted for by the utilization of apo-E normally found at higher densities.

Mechanism of heparin and serum lipoprotein interaction: Effects of calcium, phosphorylcholine, and a serum fraction

1978 ◽  
Vol 56 (7) ◽  
pp. 746-752 ◽  
Author(s):  
Sailen Mookerjea
Keyword(s):  
Serum Lipoprotein ◽  
Low Density Lipoproteins ◽  
Precipitation Reaction ◽  
Low Density ◽  
Mechanism Of Formation ◽  
Very Low Density Lipoproteins ◽  
Rat Serum ◽  
Protein Factor ◽  
Insoluble Complex ◽  
Lipoprotein Complex

The mechanism of formation of an insoluble complex between heparin and rat serum lipoprotein has been studied. Optical density changes during the reaction, counting of the fatty acid labelled lipoproteins in the precipitates, and complexing of [14C]palmitate-labelled lipoprotein with heparin–CNBr–Sepharose were used to quantitatively determine the formation of insoluble complexes. The maximal heparin–lipoprotein complex formation requires 25–30 mM of Ca2+, but with micromolar amounts of phosphorylcholine, the reaction was saturated at only 10 mM of Ca2+. The effect of phosphorylcholine in promoting the reaction was lost when purified chylomicrons or very low density lipoproteins were used. The effect of phosphorylcholine in promoting the interaction between heparin and pure chylomicrons or very low density lipoproteins was regained when a crude serum protein factor of unwashed chylomicrons was added to the system, suggesting that rat serum contains a protein factor(s) which normally inhibits the heparin–lipoprotein interaction by raising the requirement for Ca2+. Phosphorylcholine counteracted the effect of this protein, thereby favouring the precipitation reaction in the presence of much lower concentration of Ca2+. The results have been discussed with special reference to the possibility of a relationship between mucopolysaccharides, Ca2+, lipoproteins, and arterial phospholipids in the pathogenesis of atherosclerosis.

A comparison of some immunological characteristics of very low density lipoproteins of normal and hypercholesterolemic rat sera

1978 ◽  
Vol 56 (6) ◽  
pp. 673-683 ◽  
Author(s):  
Peter J. Dolphin ◽  
Laurence Wong ◽  
David Rubinstein
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Normal Serum ◽  
Low Density Lipoproteins ◽  
High Density Lipoproteins ◽  
Low Density ◽  
Very Low Density Lipoproteins ◽  
Rat Serum ◽  
Apo B ◽  
Apo E

The immunological characteristics of very low density lipoproteins (VLDL) from normal and hypercholesterolemic rat sera were compared using polyspecific antisera to VLDL and high density lipoproteins (HDL) and monospecific antisera to apo-B, apo-C, apo-A-I, and apo-E. Ultracentrifugally isolated VLDL from normal serum were studied by immunodiffusion and found to contain both discrete and associated (with apo-B) apo-C and apo-E, probably in the form of lipid-containing lipoproteins. However, immunoelectrophoresis of whole serum revealed only an associated form of the lipoprotein having pre-β mobility (i.e., VLDL), suggesting that the presence of discrete lipoproteins in isolated VLDL, each containing a single apoprotein family, may represent ultracentrifugal artifacts. Ultracentrifugally isolated VLDL from diet-induced hypercholesterolemic rat serum contained only trace amounts of apo-C and large quantities of apo-E, both of which were totally associated with apo-B. VLDL isolated by ultracentrifugation from perfusate of normal and hypercholesterolemic livers contained only associated lipoprotein complexes made up of apo-B, apo-C, and apo-E in the former but only apo-B and apo-E in the latter. These data suggest that normal VLDL are secreted as lipoprotein complexes containing apo-B, apo-C, and apo-E which may become destabilized in the circulation. However, VLDL from hypercholesterolemic serum show a marked diminution in the quantity of apo-C as indicated by the relative incorporation of [3H]leucine in vivo and by polyacrylamide gel electrophoresis of apo-VLDL.

The Influence of Apolipoprotein E on the Interactions between Normal Human Very Low Density Lipoproteins and U937 Human Macrophages: Heterogeneity among Persons

1996 ◽  
Vol 1 (1) ◽  
pp. 9-18 ◽  
Author(s):  
Frank M Sacks ◽  
Gregory P Krukonis
Keyword(s):  
Apolipoprotein E ◽  
Binding Activity ◽  
Low Density Lipoproteins ◽  
Similar Proportion ◽  
Low Density ◽  
U937 Cells ◽  
Cell Binding ◽  
Very Low Density Lipoproteins ◽  
Apo E ◽  
Normal Human

Apolipoprotein E (apo E) can mediate the cell binding of normal human very low density lipoproteins (VLDL). However, the extent to which apo E is involved in the cell binding and uptake of VLDL from different normolipidemic persons is not well defined. The VLDL ( d< 1.006 g/I) of eight subjects were fractionated into VLDL with apo E and without apo E using a monoclonal antibody that binds to the LDL receptor recognition region of apo E. VLDL particles that expressed the 1D7 binding region of apo E comprised an average of 34% (range 7–51%) of the VLDL particles. Anti-apo E blocked an average of 43% (range 8–63%) of the binding of unfractionated VLDL to U937 cells. Anti-apo E blocked a similar proportion of binding to U937 cells of three VLDL subfractions of different density ranges (Sf20–60, Sf60–100, Sf100–400). The proportion of the VLDL particles that contained apo E correlated with the extent of uptake of the total VLDL by U937 cells, but not with stimulation by total VLDL of cholesterol ester formation. The binding to cells of VLDL without apo E varied by six-fold among persons, and caused most of the binding of the total VLDL of some subjects. Therefore, normolipidemic VLDL contains particles across its density range that use apo E to bind to U937 macrophages. In some VLDL samples, apo E provides most of the cell binding activity, whereas in others the binding activity occurs by other means.

The synthesis of apoproteins of very low density lipoproteins isolated from the Golgi apparatus of rat liver

1976 ◽  
Vol 54 (7) ◽  
pp. 617-628 ◽  
Author(s):  
A. Christine Nestruck ◽  
David Rubinstein
Keyword(s):  
Golgi Apparatus ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Low Density Lipoproteins ◽  
Polyacrylamide Gel ◽  
Low Density ◽  
Very Low Density Lipoproteins ◽  
Apo B ◽  
Relationship Analysis ◽  
Discontinuous Sucrose Gradient

The incorporation of [3H]leucine in vivo into very low density lipoproteins (VLDL) from the rat hepatic Golgi apparatus and serum was studied. A Golgi-rich fraction isolated on a discontinuous sucrose gradient between 0.5 and 1.1 M was found to contain VLDL having common antigenic determinants with serum VLDL. The incorporation of the [3H]leucine into the Golgi VLDL and serum VLDL suggested a precursor–product relationship. Analysis of the apoproteins of the Golgi VLDL by polyacrylamide gel electrophoresis revealed protein bands with similar mobility to those of serum VLDL, except that the former contained virtually no rapidly migrating peptides with the mobility of serum apo-C-II and apo-C-III. The pattern of incorporation of the [3H]leucine into the apoproteins was similar in VLDL from Golgi apparatus and serum, except for the absence of radioactivity in the area of the gel of Golgi apo-VLDL corresponding to apo-C-II and apo-C-III. The radioactive amino acid was incorporated predominantly into the Golgi apo-VLDL bands with similar mobility to apo-B and an apoprotein or group of apoproteins containing the arginine-rich peptide of serum VLDL. In vitro incubation of the Golgi VLDL with [3H]leucine-labeled HDL resulted in the acquisition of a number of proteins, including the rapidly migrating proteins. Administration of colchicine prior to the injection of [3H]leucine resulted in the appearance of gel bands and radioactivity in the apo-C-II and apo-C-III areas of Golgi apo-VLDL, suggesting that these can be acquired if secretion of VLDL is slowed or inhibited. The hepatic Golgi apparatus was then divided into fractions of predominantly forming face (GF3) or secretory granules (GF1). After polyacrylamide gel electrophoresis of the apo-VLDL from GF3, no visible bands or incorporation of [3H]leucine was found in the region of apo-C-II or apo-C-III. However VLDL from GF1 showed visible and radioactive bands in the apo-C-II and apo-C-III area although they represented a much smaller proportion of the total apoprotein than was found in the corresponding serum apo-VLDL. In the isolated perfused liver the percentage incorporation of [3H]leucine into the rapidly migrating apoproteins of Golgi VLDL was considerably less than that found in the corresponding apoproteins of perfusate VLDL, where circulating C lipoproteins are virtually absent.The data indicate that nascent VLDL begins to acquire the C-II and C-III apoproteins during its passage through the Golgi apparatus but that the main acquisition occurs during or after secretion into the space of Disse.

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