Hepatic metabolism of oxidatively modified apo E-free high-density lipoproteins.
OBJECTIVE
The metabolism of rat apo E-free high-density lipoproteins (HDL) was contrasted with oxidatively modified apo E-free high-density lipoproteins (OX-HDL) in the rat hepatoma cell, Fu5AH.


RESULTS
When 10-100 microg/ml [125I]-HDL or [125I]-OX-HDL were incubated with cells for 4 h at 37 degrees C, cellular uptake of oxidized lipoproteins was twice control. In contrast, protein degradation was equal. [125I]-HDL or [125I]-OX-HDL were incubated with the cells for 4 h followed by a 4 h chase with unlabeled HDL and OX-HDL, respectively. In these experiments, 80% of [125I]-HDL was resecreted from the cell within 30 min while 50% of [125I]-OX-HDL was retained by the cell after 2 h. Electron microscopy was used to determine if the OX-HDL was retained in lysosomes. Cells were incubated with gold-labeled OX-HDL, and lysosomes were stained with acid phosphatase. Gold-labeled OX-HDL was abundant in intracellular vesicles that were not reactive to acid phosphatase. However, vesicles with a high content of OX-HDL frequently stained positively for 3,3'-diaminobenzidine, a stain that reacts with catalase and is used to detect peroxisomes.


CONCLUSIONS
The present evidence indicates that the cellular metabolism of OX-HDL is different from that of unmodified HDL.
Department of Physiology, Louisiana State University Medical Center, New Orleans 70112, USA.
J G
JG
DeLamatre
D M
DM
Gabaldon
C S
CS
Arnold
T G
TG
Sarphie
C A
CA
Hornick
D000818:Animals; D001057:Apolipoproteins E / Q000378:metabolism*; D002478:Cells, Cultured; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008099:Liver / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D010084:Oxidation-Reduction; D051381:Rats; D017207:Rats, Sprague-Dawley
D001057:Apolipoproteins E; D008075:Lipoproteins, HDL