125I-insulin internalization by perfused rat liver: Comparison of its subcellular distribution with that of a lysosomally targeted molecule, 125I-asialofetuin

W. F. Ward

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

The subcellular distribution of 125I-insulin in the perfused rat liver was compared with the subcellular distribution of the lysosomally targeted asialoglycoprotein, 125I-asialofetuin. The use of Percoll density gradient medium provided excellent separation of lysosomes from the subcellular membrane fractions. Following perfusion with 125I-asialofetuin, a distinct peak of TCA-precipitable radioactivity could be observed in the lysosomal region of the gradient. In contrast, the gradient distribution of TCA-precipitable radioactivity following perfusion with physiological concentrations of 125I-insulin was unimodal, the observed peak corresponding to the distribution of intracellular membrane marker enzymes. Leupeptin, an inhibitor of lysosomal proteolysis, inhibited the degradation of 125I-asialofetuin but had no effect on 125I-insulin degradation. In addition, leupeptin produced a marked increase in TCA-precipitable radioactivity in the lysosome rich region of gradients prepared from livers perfused with 125I-asialofetuin. No such effect was observed following perfusion with 125I-insulin. These findings are consistent with an initial localization of the internalized insulin molecule with the membraneous system of the liver cell rather than the lysosomal system.

Original languageEnglish (US)
Pages (from-to)509-512
Number of pages4
JournalHormone and Metabolic Research
Volume16
Issue number10
DOIs
StatePublished - Jan 1 1984

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical

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