Alterations in the structure, physicochemical properties, and pH of hepatocyte lysosomes in experimental iron overload

Brent M. Myers, Franklyn G. Prendergast, Ralph Holman, Susan M. Kuntz, Nicholas F La Russo

Research output: Contribution to journalArticle

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Abstract

While hemochromatosis is characterized by sequestration of iron-protein complexes in hepatocyte lysosomes, little is known about the effects of excess iron on these organelles. Therefore, we studied the effects of experimental iron overload on hepatocyte lysosomal structure, physicochemical properties, and function in rats fed carbonyl iron. A sixfold increase (P < 0.0001) in hepatic iron and a fivefold increase in lysosomal iron (P < 0.01) was observed after iron loading; as a result, hepatocyte lysosomes became enlarged and misshapen. These lysosomes displayed increased (P < 0.0001) fragility; moreover, the fluidity of lysosomal membranes isolated from livers of iron-loaded rats was decreased (P < 0.0003) as measured by fluorescence polarization. Malondialdehyde, an end product of lipid peroxidation, was increased by 73% (P < 0.008) in lysosomal membranes isolated from livers of iron-overloaded rats. While amounts of several individual fatty acids in isolated lysosomal membranes were altered after iron overload, cholesterol/ phospholipid ratios, lipid/protein ratios, double-bond index, and total saturated and unsaturated fatty acids remained unchanged. The pH of lysosomes in hepatocytes isolated from livers of iron-loaded rats and measured by digitized video microscopy was increased (control, 4.70 ± 0.05; iron overload, 5.21 ± 0.10; P < 0.01). Our results demonstrate that experimental iron overload causes marked alterations in hepatocyte lysosomal morphology, an increase in lysosomal membrane fragility, a decrease in lysosomal membrane fluidity, and an increase in intralysosomal pH. Iron-catalyzed lipid peroxidation is likely the mechanism of these structural, physicochemical, and functional disturbances.

Original languageEnglish (US)
Pages (from-to)1207-1215
Number of pages9
JournalJournal of Clinical Investigation
Volume88
Issue number4
StatePublished - 1991

Fingerprint

Iron Overload
Lysosomes
Hepatocytes
Iron
Membrane Fluidity
Liver
Lipid Peroxidation
Membranes
Fatty Acids
Video Microscopy
Fluorescence Polarization
Hemochromatosis
Malondialdehyde
Unsaturated Fatty Acids
Organelles
Phospholipids
Proteins
Cholesterol
Lipids

Keywords

  • Hemochromatosis
  • Lipid peroxidation
  • Organelle damage

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Alterations in the structure, physicochemical properties, and pH of hepatocyte lysosomes in experimental iron overload. / Myers, Brent M.; Prendergast, Franklyn G.; Holman, Ralph; Kuntz, Susan M.; La Russo, Nicholas F.

In: Journal of Clinical Investigation, Vol. 88, No. 4, 1991, p. 1207-1215.

Research output: Contribution to journalArticle

Myers, Brent M. ; Prendergast, Franklyn G. ; Holman, Ralph ; Kuntz, Susan M. ; La Russo, Nicholas F. / Alterations in the structure, physicochemical properties, and pH of hepatocyte lysosomes in experimental iron overload. In: Journal of Clinical Investigation. 1991 ; Vol. 88, No. 4. pp. 1207-1215.
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