SECRETION OF VERY LOW DENSITY LIPOPROTEINS (VLDL) ENRICHED IN CHOLESTEROL ESTERS BY CULTURED RAT HEPATOCYTES DURING STIMULATION OF INTRACELLULAR CHOLESTEROL ESTERIFICATION

1981 ◽  
Vol 9 (2) ◽  
pp. 184P-184P
Author(s):  
Christian A. Drevon ◽  
Sheldon C. Engelhorn ◽  
Daniel Steinberg
Keyword(s):  
Rat Hepatocytes ◽  
Low Density Lipoproteins ◽  
Cholesterol Esterification ◽  
Low Density ◽  
Cholesterol Esters ◽  
Very Low Density Lipoproteins ◽  
Cultured Rat Hepatocytes ◽  
Intracellular Cholesterol ◽  
Stimulation Of

scholarly journals Lysophosphatidylcholine metabolism and lipoprotein secretion by cultured rat hepatocytes deficient in choline

1989 ◽  
Vol 260 (1) ◽  
pp. 207-214 ◽  
Author(s):  
B S Robinson ◽  
Z Yao ◽  
D J Baisted ◽  
D E Vance
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Rat Hepatocytes ◽  
Cellular Protein ◽  
Low Density Lipoproteins ◽  
Low Density ◽  
Very Low Density Lipoproteins ◽  
Phosphatidylcholine Biosynthesis ◽  
Cultured Rat Hepatocytes ◽  
Phosphatidylcholine Synthesis

The metabolism of lysophosphatidylcholine was studied in cultured rat hepatocytes deficient in choline and methionine. Even though the cells were defective in phosphatidylcholine biosynthesis, the albumin-stimulated release of lysophosphatidylcholine (1.9 nmol/h per mg of cellular protein) was similar to that in hepatocytes supplemented with choline. Albumin also stimulated (1.4-fold) the release of phosphatidylcholine from the deficient cells. The extra phosphatidylcholine and lysophosphatidylcholine in the medium were largely recovered in the albumin fraction (density greater than 1.18 g/ml), suggesting that albumin released these lipids from hepatocytes because of binding to this protein. The secretion of glycerophosphocholine was decreased by about 40% by the addition of albumin. When choline-deficient hepatocytes were supplemented with lysophosphatidylcholine, it was transported into the cells and mainly acylated to form phosphatidylcholine, which increased in mass by 30-35% in the first 4 h of incubation. Lysophosphatidylcholine was shown to be as effective as choline in restoring the secretion of very-low-density lipoproteins to normal amounts, as judged by the secretion of triacylglycerol, phosphatidylcholine and the apolipoproteins associated with very-low-density lipoproteins. Thus phosphatidylcholine synthesis via reacylation of lysophosphatidylcholine, via the CDP-choline pathway or via methylation of phosphatidylethanolamine, will satisfy the requirements for secretion of very-low-density lipoprotein from hepatocytes.

scholarly journals Unaltered catabolism of desialylated low-density lipoprotein in the pig and in cultured rat hepatocytes

1979 ◽  
Vol 180 (3) ◽  
pp. 647-654 ◽  
Author(s):  
A D Attie ◽  
D B Weinstein ◽  
H H Freeze ◽  
R C Pittman ◽  
D Steinberg
Keyword(s):  
Sialic Acid ◽  
Clostridium Perfringens ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Rat Hepatocytes ◽  
Low Density Lipoproteins ◽  
Low Density ◽  
Rapid Clearance ◽  
Cultured Rat Hepatocytes ◽  
Extrahepatic Tissues

Removal of the terminal sialic acid residues from many serum glycoproteins results in exposure of their penultimate galactose residues and rapid clearance from circulation by the liver. Low-density lipoprotein is a glycoprotein containing 21 galactose and 9 sialic acid residues per particle. Studies in this laboratory and others have shown that both the liver and extrahepatic tissues contribute to the degradation of low-density lipoprotein. This study was undertaken to determine whether desialylation of pig low-density lipoprotein alters its removal from circulation. Low-density lipoprotein was incubated at 37 degrees C with an agarose-bound neuraminidase, proteinase-free, from Clostridium perfringens. After 18 h at pH 5.0, 70% of the sialic acid residues were removed. The desialylated 131I-labelled and native 125I-labelled low-density lipoproteins were simultaneously injected into a pig, and their disappearance from plasma was followed for 96 h. The turnovers of the two were identical. In contrast, neuraminidase-treated fetuin was cleared about 200-fold faster than native fetuin. Studies were also performed in cultured rat hepatocytes. Rates of degradation of native and neuraminidase-treated low-density lipoprotein were similar, whereas asialo-fetuin was degraded at six to ten times the rate of native fetuin. Thus desialylation does not appear to alter low-density-lipoprotein catabolism by hepatic or extrahepatic cells.

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