Identification of fibroblasts as a major site of albumin catabolism in peripheral tissues

J. L. Strobel, S. G. Cady, T. K. Borg, L. Terracio, J. W. Baynes, S. R. Thorpe

Research output: Contribution to journalArticlepeer-review

Abstract

Rat serum albumin has been labeled with dilactitol-125I-tyramine, (125I-DLT) a radioactive tracer which remains entrapped within lysosomes following cellular uptake and degradation of the carrier protein. Similar kinetics of clearance from the rat circulation were observed for albumin labeled conventionally with 125I or 125I-DLT-albumin, both proteins having circulating half-lives of ~2.2 days. In contrast, the recovery of whole body radioactivity had half-lives of ~2.2 and 5.1 days, respectively, for the two protein preparations, indicating substantial retention of degradation products derived from catabolism of 125I-DLT-albumin. Measurement of total and acid-soluble radioactivity in tissues 2 or 4 days after injection of 125I-DLT-albumin revealed that skin and muscle accounted for the largest fraction (50-60%) of degradation products in the body. Fibroblasts were identified by autoradiography as the major cell type containing radioactive degradation products in skin and muscle. Fibroblasts were isolated from skin by collagenase digestion, followed by density gradient centrifugation. The amount of acid-soluble radioactivity recovered in these cells was in excellent agreement with that predicted based on acid precipitation of solubilized whole skin preparations. These studies demonstrate for the first time that fibroblasts are a major cell type involved in the degradation of albumin in vivo.

Original languageEnglish (US)
Pages (from-to)7989-7994
Number of pages6
JournalJournal of Biological Chemistry
Volume261
Issue number17
StatePublished - 1986

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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