Hepatic metabolism of oxidatively modified apo E-free high-density lipoproteins

Authors

  • John G. DeLamatre,

    Corresponding author
    1. Department of Physiology, Division of Lipoprotein Metabolism and Pathophysiology, Louisiana State University Medical Center, New Orleans, LA, USA
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  • Donna M. Gabaldon,

    1. Department of Physiology, Division of Lipoprotein Metabolism and Pathophysiology, Louisiana State University Medical Center, New Orleans, LA, USA
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  • C. Shane Arnold,

    1. Department of Physiology, Division of Lipoprotein Metabolism and Pathophysiology, Louisiana State University Medical Center, New Orleans, LA, USA
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  • T. G. Sarphie,

    1. Department of Anatomy, Louisiana State University Medical Center, New Orleans, LA, USA
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  • Conrad A. Hornick

    1. Department of Physiology, Division of Lipoprotein Metabolism and Pathophysiology, Louisiana State University Medical Center, New Orleans, LA, USA
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Department of Physiology, Division of Lipoprotein Metabolism and Pathophysiology, Louisiana State University Medical Center, 1542 Tulane Avenue, New Orleans, LA 70112, USA

Abstract

ABSTRACT—Aims/Background: 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 μg/ml [125I]-HDL or [125I]-OX-HDL were incubated with cells for 4 h at 37°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.

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