Cell density-dependent mitogenic effect and -independent cellular handling of epidermal growth factor in primary cultured rat hepatocytes

Teruki Hamada, Yukio Kato, Tetsuya Terasaki, Yuichi Sugiyama

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Aims: Mitogenic effect and cellular handling of epidermal growth factor (EGF) were analyzed in primary cultured rat hepatocytes at several cell densities. Methods/Results: DNA synthesis, assessed by the incorporation of 125I-deoxyuridine, was accelerated by EGF at a low cell density while that stimulated by EGF was relatively low at the highest cell density, suggesting a cell density-dependent regulation of mitogenic response to EGF. An equilibrium binding study of 125I-EGF in the presence of various concentrations of unlabeled EGF at 0°C revealed that the dissociation constant (K(d)) was 0.47-0.88 nM while the specific binding capacity (n) was 86-96 fmol/mg protein at each cell density. No significant difference was observed in the time profiles of the surface-bound, internalized, and degradation products of 125I-EGF, assessed per mg protein, between different cell densities. Based on a kinetic analysis of the time-profiles, the internalization rate constant and the degradation rate constant were found to be independent of cell density. Conclusions: These results indicate that the cellular binding and disposition of EGF are not regulated by cell density, and that the cell density-dependence of the mitogenic effect cannot be attributed to differences in the affinity or capacity of the EGF receptor, internalization, or degradation of EGF. We speculate that the cell density-dependent mitogenic response may be accounted for by the difference in other factors such as the signal transduction processes induced by the receptor binding of EGF, or the translocation of a small fraction of the total EGF to hepatocyte nuclei.

Original languageEnglish
Pages (from-to)353-360
Number of pages8
JournalJournal of Hepatology
Volume26
Issue number2
DOIs
Publication statusPublished - 1997 Feb
Externally publishedYes

Keywords

  • degradation
  • epidermal growth factor
  • hepatocyte
  • internalization
  • mitogenic response

ASJC Scopus subject areas

  • Hepatology

Fingerprint Dive into the research topics of 'Cell density-dependent mitogenic effect and -independent cellular handling of epidermal growth factor in primary cultured rat hepatocytes'. Together they form a unique fingerprint.

Cite this