Hepatic uptake and metabolism of chylomicron retinyl esters: Probable role of plasma membrane/endosomal retinyl ester hydrolases

E. H. Harrison, M. Z. Gad, A. Catharine Ross

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

Previous studies have indicated the presence of both neutral and acid, bile salt-independent retinyl ester hydrolases associated with plasma membrane and endosome fractions of rat liver homogenates. In the present studies, chylomicrons containing tritium-labeled retinyl esters were injected intravenously into rats in order to study the initial metabolism of retinyl esters during and after uptake into the liver. At various times after chylomicron injection, plasma was obtained and the liver was homogenized and subjected to analytical subcellular fractionation. Labeled retinyl esters were rapidly cleared from plasma (half-time ≃ 10 min) and appeared in the liver. Within the liver, label first appeared in plasma membrane/endosomal fractions that were also enriched in both neutral and acid, bile salt- independent retinyl ester hydrolase activities. At no time were the labeled esters significantly associated with fractions enriched in lysosomes. Rather, it appeared that the labeled esters were hydrolyzed and/or transferred to fractions enriched in endoplasmic reticulum. These studies demonstrate the co-localization of newly delivered retinyl esters and bile salt-independent retinyl ester hydrolase enzyme activities and thus, suggest a probable role for these enzymes in the initial hepatic metabolism of chylomicron retinyl esters. This conclusion was further supported by the observation that plasma membrane/endosomal fractions were active in catalyzing the hydrolysis of chylomicron remnant retinyl esters in vitro.

Original languageEnglish (US)
Pages (from-to)1498-1506
Number of pages9
JournalJournal of Lipid Research
Volume36
Issue number7
StatePublished - 1995

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Chylomicrons
Cell membranes
Metabolism
Esters
Cell Membrane
Liver
Bile Acids and Salts
Rats
Chylomicron Remnants
Plasmas
Tritium
retinyl esterase
Endosomes
Enzyme activity
Enzymes
Fractionation
Lysosomes
Endoplasmic Reticulum
Labels
Hydrolysis

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Endocrinology
  • Cell Biology

Cite this

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abstract = "Previous studies have indicated the presence of both neutral and acid, bile salt-independent retinyl ester hydrolases associated with plasma membrane and endosome fractions of rat liver homogenates. In the present studies, chylomicrons containing tritium-labeled retinyl esters were injected intravenously into rats in order to study the initial metabolism of retinyl esters during and after uptake into the liver. At various times after chylomicron injection, plasma was obtained and the liver was homogenized and subjected to analytical subcellular fractionation. Labeled retinyl esters were rapidly cleared from plasma (half-time ≃ 10 min) and appeared in the liver. Within the liver, label first appeared in plasma membrane/endosomal fractions that were also enriched in both neutral and acid, bile salt- independent retinyl ester hydrolase activities. At no time were the labeled esters significantly associated with fractions enriched in lysosomes. Rather, it appeared that the labeled esters were hydrolyzed and/or transferred to fractions enriched in endoplasmic reticulum. These studies demonstrate the co-localization of newly delivered retinyl esters and bile salt-independent retinyl ester hydrolase enzyme activities and thus, suggest a probable role for these enzymes in the initial hepatic metabolism of chylomicron retinyl esters. This conclusion was further supported by the observation that plasma membrane/endosomal fractions were active in catalyzing the hydrolysis of chylomicron remnant retinyl esters in vitro.",
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Hepatic uptake and metabolism of chylomicron retinyl esters : Probable role of plasma membrane/endosomal retinyl ester hydrolases. / Harrison, E. H.; Gad, M. Z.; Ross, A. Catharine.

In: Journal of Lipid Research, Vol. 36, No. 7, 1995, p. 1498-1506.

Research output: Contribution to journalArticle

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