scholarly journals Effects of preincubation of primary monolayer cultures of rat hepatocytes with low- and high-density lipoproteins on the subsequent binding and metabolism of human low-density lipoprotein

1987 ◽  
Vol 247 (1) ◽  
pp. 79-84 ◽  
Author(s):  
A M Salter ◽  
M Bugaut ◽  
J Saxton ◽  
S C Fisher ◽  
D N Brindley
Keyword(s):  
Metabolic Regulation ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Rat Hepatocytes ◽  
High Density ◽  
High Density Lipoproteins ◽  
Low Density ◽  
Primary Monolayer ◽  
Human High Density Lipoprotein ◽  
Primary Monolayer Cultures

1. There are two distinct binding sites (Site 1 and Site 2) for human low-density lipoprotein (LDL) on rat hepatocytes in monolayer culture [Salter, Saxton & Brindley (1986) Biochem. J. 240, 549-557]. 2. Binding of 125I-LDL to Site 1, but not to Site 2, is up-regulated between 20 and 44 h in culture by preincubation of the cells with human high-density lipoprotein 3 (HDL3). 3. A similar preincubation with HDL2 had no significant effect on binding to either site. 4. Preincubation with human LDL led to a partial down-regulation of subsequent binding of 125I-LDL to Site 1. Since binding after incubation with LDL was measured at 37 degrees C, binding to Site 2 could not be distinguished from LDL that had been internalized by the cells. 5. Hepatocytes were shown to degrade 125I-LDL, resulting in the accumulation of [125I]iodotyrosine in the medium. Evidence was found that iodotyrosine may be further degraded by deiodinase produced by the cells. 6. Regulation of binding to Site 1 by preincubation with LDL or HDL3 was found to lead to a parallel regulation of LDL degradation. 7. It is concluded that rat hepatocytes not only bind but also metabolize human LDL and that these processes are under metabolic regulation.

scholarly journals Glycosylation of apolipoproteins by cultured rat hepatocytes. Effect of tunicamycin on lipoprotein secretion

1981 ◽  
Vol 200 (2) ◽  
pp. 409-414 ◽  
Author(s):  
J Bell-Quint ◽  
T Forte ◽  
P Graham
Keyword(s):  
Low Density Lipoprotein ◽  
Specific Inhibitor ◽  
Density Lipoprotein ◽  
Rat Hepatocytes ◽  
High Density ◽  
Protein Glycosylation ◽  
High Density Lipoproteins ◽  
Low Density ◽  
Apolipoprotein C ◽  
Cultured Rat Hepatocytes

Cultured rat hepatocytes were used to measure hepatic synthesis of rat plasma glycoproteins. [3H]Glucosamine was progressively incorporated into the protein of hepatocyte culture media very-low-density lipoprotein, low-density lipoprotein, high-density lipoprotein and the p greater than 1.21 g/ml fraction after 3.5 and 6.5 h incubation. Apolipoproteins B, E and C, as well as transferrin, were identified as glycoproteins. The association of radioactivity with apolipoprotein C of hepatocyte very-low-density and high-density lipoproteins suggests that apolipoprotein C-III-3, the only C apoglycoprotein in the rat, is synthesized de novo by the hepatocytes. Treatment of hepatocytes with tunicamycin, a specific inhibitor of protein glycosylation, resulted in a substantial decrease in [3H]glucosamine incorporation into hepatocyte very-low-density, low-density and high-density lipoproteins and p greater than 1.21 g/ml protein, but had little or no effect on secretion. In the rat, hepatic secretion of lipoproteins and transferrin does not appear to be dependent on prior protein glycosylation.

scholarly journals Stimulation of apolipoprotein secretion in very-low-density and high-density lipoproteins from cultured rat hepatocytes by dexamethasone

1990 ◽  
Vol 271 (3) ◽  
pp. 575-583 ◽  
Author(s):  
P Martin-Sanz ◽  
J E Vance ◽  
D N Brindley
Keyword(s):  
Low Density Lipoprotein ◽  
Lipoprotein Metabolism ◽  
Density Lipoprotein ◽  
Rat Hepatocytes ◽  
High Density ◽  
High Density Lipoproteins ◽  
Low Density ◽  
Apo B ◽  
Apo E ◽  
The Masses

The effects of dexamethasone (a synthetic glucocorticoid) and insulin on the secretion of very-low-density lipoprotein (VLDL) and high-density lipoprotein (HDL) were investigated. Rat hepatocytes in monolayer culture were preincubated for 15 h in the presence or absence of combinations of 100 nM-dexamethasone and 2 nM-, 10 nM- or 50 nM-insulin. Dexamethasone increased [3H]oleate incorporation into secreted triacylglycerol by 2.7-fold and the mass of triacylglycerol secreted by 1.5-fold. Insulin alone decreased these parameters and antagonized the effect of dexamethasone. Dexamethasone increased the secretion of [3H]leucine in apolipoprotein (apo) E, and in the large (BH) and small (BI) forms of apo B in VLDL by about 7.1-, 3.6- and 4.0-fold respectively. Insulin alone decreased the secretion of these 3H-labelled apolipoproteins in VLDL. However, 2 nM-insulin with dexamethasone increased the secretion of 3H-labelled apo BH and apo BL by a further 0.8- and 3.2-fold respectively; 50 nM-insulin decreased the secretions of apo E, apo BH and apo BL in VLDL. Similar effects for dexamethasone or insulin alone were also obtained for the masses of apo E and apo BL + H secreted in VLDL. Albumin secretion was not significantly altered by either dexamethasone or insulin alone, but in combination they stimulated by 2.1-2.6-fold. Insulin or dexamethasone alone had little effect on the secretion of apolipoproteins in the HDL fraction. However, dexamethasone plus 2 nM-insulin increased the incorporation of [3H]leucine into apo AI, apo AH plus apo C, apo AIV and apo E of HDL by about 1.8-, 1.6-, 1.7- and 2.0-fold respectively. The apo E in the bottom fraction represented about 69% of the total 3H-labelled apo E secreted. The responses in the total secretion of apo E from the hepatocytes resembled those seen in HDL. The interactions of insulin and dexamethasone are discussed in relation to the general regulation of lipoprotein metabolism, the development of hyperlipidaemias and the predisposition to premature atherosclerosis.

The interaction of lipolysis products of very low density lipoprotein with plasma high density lipoprotein (HDL): perfusate HDL with plasma HDL subfractions

1987 ◽  
Vol 65 (3) ◽  
pp. 252-260 ◽  
Author(s):  
S. P. Tam ◽  
W. C. Breckenridge
Keyword(s):  
Particle Size ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
High Density ◽  
Molar Ratio ◽  
High Density Lipoproteins ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Hdl Subfractions ◽  
Apo E

The nature of the interaction of high density lipoproteins (HDL), formed during lipolysis of human very low density lipoprotein (VLDL) by perfused rat heart, with subfractions of human plasma HDL was investigated. Perfusate HDL, containing apoliproproteins (apo) E, C-II, and C-III but no apo A-I or A-II, was incubated with a subfraction of HDL (HDL-A) containing apo A-I and A-II, but devoid of apo C-II, C-III, and E. The products of the incubation were resolved by heparin-Sepharose or hydroxylapatite chromatography under conditions which allowed the resolution of the initial HDL-A and perfusate HDL. The fractions were analyzed for apolipoprotein content and lipid composition and assessed for particle size by electron microscopy. Following the incubation, the apo-E-containing lipoproteins were distinct from perfusate HDL since they contained apo A-I as a major component and apo C-II and C-III in reduced proportions. However, the HDL-A fraction contained apo C-II and C-III as major constituents. Associated with these changes in apolipoprotein composition, the apo-E-rich lipoproteins acquired cholesteryl ester from the HDL-A fraction and lost phospholipid to the HDL-A fraction. The HDL-A fraction maintained a low unesterified cholesterol/phospholipid molar ratio (0.23), while the apo-E-containing lipoproteins possessed a high ratio (0.75) characteristic of the perfusate HDL. The particle size of apo-E-containing lipoproteins (138.9 ± 22.5 Å; 1 Å = 0.1 nm) was larger than the initial HDL-A (126.5 ± 17.6 Å) or the new HDL-A-like fraction (120.9 ± 17.4 Å) obtained following incubation with perfusate HDL. It is concluded that incubation of perfusate HDL containing apo E, C-II, and C-III with plasma HDL subfractions results in the acquisition of apo A-I and cholesteryl esters by the apo-E-containing perfusate HDL and the loss of apo C-II, C-III, and phospholipid to the plasma HDL-A fraction. The process does not appear to be due to fusion of the particles, since the apo-E-containing lipoproteins maintain a cholesterol/phospholipid ratio distinct from the HDL-A fraction. The data provide evidence for a potential mechanism for the formation of HDL-E, an apo-E-containing lipoprotein of HDL size and density, through lipolysis of VLDL.

scholarly journals The sites of degradation of rat high-density-lipoprotein apolipoprotein E specifically labelled with O-(4-diazo-3-[125I]iodobenzoyl)sucrose

1985 ◽  
Vol 226 (3) ◽  
pp. 715-721 ◽  
Author(s):  
F M Van't Hooft ◽  
A Van Tol
Keyword(s):  
Serum Proteins ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
High Density ◽  
High Density Lipoproteins ◽  
Low Density ◽  
Serum Lipoproteins ◽  
Rat Serum ◽  
Apo E ◽  
Fasted Rats

O-(4-Diazo-3-[125I]iodobenzoyl)sucrose ([125I]DIBS), a novel labelling compound specifically designed to study the catabolic sites of serum proteins [De Jong, Bouma, & Gruber (1981) Biochem. J. 198, 45-51], was applied to study the tissue sites of degradation of serum lipoproteins. [125I]DIBS-labelled apolipoproteins (apo) E and A-I, added in tracer amounts to rat serum, associate with high-density lipoproteins (HDL) just like conventionally iodinated apo E and A-I. No difference is observed between the serum decays of chromatographically isolated [125I]DIBS-labelled and conventionally iodinated HDL labelled specifically in either apo E or apo A-I. When these specifically labelled HDLs are injected into fasted rats, a substantial [125I]DIBS-dependent 125I accumulation occurs in the kidneys and in the liver. No [125I]DIBS-dependent accumulation is observed in the kidneys after injection of labelled asialofetuin or human low-density lipoprotein. It is concluded that the kidneys and the liver are important sites of catabolism of rat HDL apo E and A-I.

scholarly journals Association of the Endotoxin Antagonist E5564 with High-Density Lipoproteins In Vitro: Dependence on Low-Density and Triglyceride-Rich Lipoprotein Concentrations

2003 ◽  
Vol 47 (9) ◽  
pp. 2796-2803 ◽  
Author(s):  
Kishor M. Wasan ◽  
Olena Sivak ◽  
Richard A. Cote ◽  
Aaron I. MacInnes ◽  
Kathy D. Boulanger ◽  
...  
Keyword(s):  
Human Plasma ◽  
Human Subjects ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
High Density ◽  
High Density Lipoproteins ◽  
Low Density ◽  
Distribution Profile ◽  
Transfer Activity

ABSTRACT The objective of this study was to determine the distribution profile of the novel endotoxin antagonist E5564 in plasma obtained from fasted human subjects with various lipid concentrations. Radiolabeled E5564 at 1 μM was incubated in fasted plasma from seven human subjects with various total cholesterol (TC) and triglyceride (TG) concentrations for 0.5 to 6 h at 37°C. Following these incubations, plasma samples were separated into their lipoprotein and lipoprotein-deficient fractions by ultracentrifugation and were assayed for E5564 radioactivity. TC, TG, and protein concentrations in each fraction were determined by enzymatic assays. Lipoprotein surface charge within control and phosphatidylinositol-treated plasma and E5564’s influence on cholesteryl ester transfer protein (CETP) transfer activity were also determined. We observed that the majority of E5564 was recovered in the high-density lipoprotein (HDL) fraction. We further observed that incubation in plasma with increased levels of TG-rich lipoprotein (TRL) lipid (TC and TG) concentrations resulted in a significant increase in the percentage of E5564 recovered in the TRL fraction. In further experiments, E5564 was preincubated in human TRL. Then, these mixtures were incubated in hypolipidemic human plasma for 0.5 and 6 h at 37°C. Preincubation of E5564 in purified TRL prior to incubation in human plasma resulted in a significant decrease in the percentage of drug recovered in the HDL fraction and an increase in the percentage of drug recovered in the TRL and low-density lipoprotein fractions. These findings suggest that the majority of the drug binds to HDLs. Preincubation of E5564 in TRL prior to incubation in normolipidemic plasma significantly decreased the percentage of drug recovered in the HDL fraction. Modifications to the lipoprotein negative charge did not alter the E5564 concentration in the HDL fraction. In addition, E5564 does not influence CETP-mediated transfer activity. Information from these studies could be used to help identify the possible components of lipoproteins which influence the interaction of E5564 with specific lipoprotein particles.

scholarly journals The Content of Low Density Lipoprotein, High Density Lipoproteins, Cholesterol on Pen Shells (Atrina Pectinata) Fish Catch in Kenjeran Surabaya

2020 ◽  
Vol 7 (2) ◽  
pp. 51
Author(s):  
Rio Khalif Eldiaz ◽  
Agustono Agustono ◽  
Kustiawan Tri Pursetyo
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hdl Cholesterol ◽  
High Density ◽  
High Density Lipoproteins ◽  
Low Density ◽  
Digestive Organs ◽  
Cholesterol Levels ◽  
Fish Catch ◽  
Atrina Pectinata

Pen Shells (A. pectinata) Is one type of a clam that is mostly consumed, Cholesterol levels included in a category high. Although the high cholesterol levels. Shells also contain levels commonly called ldl cholesterol evil . Having shells also levels of hdl, Cholesterol levels total normal in plasma adults is of 120 until 200 mg/dl. Different from its function at the time of cholesterol levels normal, the higher cholesterol levels in the blood, the greater the risk of atherosclerosis also. The purpose of this research is to get information about ldl levels , hdl and cholesterol contained in shells kampak , as well as to determine the shells kampak who most worthy for consumption. Parameter that observed in this research was ldl , hdl , cholesterol .This study using methods descriptive against the difference levels of low density lipopprotein ( ldl ) and high-density lipoproteins ( hdl ) and cholesterol in any bivalve hatchets the results of catch fishermen in kenjeran surabaya. Average levels of ldl on pen shells (A. pictinata) In the meat is 30,990 mg/100g, in the muscle is 28,329 mg/100g and in the Digestive organs is 25,225 mg/100g ; The average levels of hdl on pen shells (A. pictinata) in the meat is 96,772 mg/100g, in the muscle is 87,139 mg/100g and in the Digestive organs is 67,516 mg/100g ; average levels of cholesterol on pen shells (A. pictinata) in the meat is 165,609 mg/100g, in the muscle is 147,382 mg/100g and in the Digestive organs is 114,551 mg/100g. Levels of LDL, HDL and cholesterol Lead to results same that is the most number are located on the meat, then muscle and at least there are on an disgestive organ.

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