Rat C6 glial cells synthesize insulin-like growth factor I (IGF-I) and express IGF-I receptors and IGF-II/mannose 6-phosphate receptors

Endocrinology. 1989 Apr;124(4):1727-36. doi: 10.1210/endo-124-4-1727.


We have used the rat C6 glial cell line as a model system to study the role of insulin-like growth factors (IGF) in neuroglial cells of the central nervous system (CNS). Northern blot analysis of C6 RNA demonstrated the presence of IGF-I mRNA and undetectable IGF-II mRNA. IGF-I and IGF-binding protein(s), but not IGF-II, were detected in C6 glial cell-conditioned medium. The level of IGF-I was 1-4 ng/ml in conditioned medium based on a human IGF-I standard. The immunoreactive IGF-I inhibited [125I]IGF-I binding to the IGF-I receptor on chick embryo fibroblasts and stimulated [3H]thymidine incorporation into chick embryo fibroblast DNA. Competitive binding and affinity cross-linking experiments using [125]IGF-I and [125I]IGF-II demonstrated the presence of IGF-I receptors (type I) and IGF-II/mannose 6-phosphate receptors (type II) on C6 glial cell membranes. An immunoglobulin (no. 3637) directed against the rat IGF-II receptor blocked the degradation of [125I]IGF-II added to C6 glial cells, presumably by blocking receptor-mediated internalization. We were unable to demonstrate an autocrine role for IGF in the C6 glial cell line, since [3H]thymidine incorporation into DNA was stimulated equally well by IGF-I-deficient rat serum and normal serum, and added IGF did not stimulate [3H]thymidine incorporation into DNA when tested alone or when added to IGF-I-deficient serum. We propose that neuroglial cell-derived IGF-I may serve as a paracrine growth stimulus in the central nervous system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Northern
  • Cell Membrane / analysis
  • Cell Membrane / ultrastructure
  • Cells, Cultured
  • DNA / biosynthesis
  • Gene Expression Regulation
  • Insulin-Like Growth Factor I / biosynthesis*
  • Insulin-Like Growth Factor I / genetics
  • Insulin-Like Growth Factor I / metabolism
  • Neuroglia / cytology*
  • Neuroglia / metabolism
  • Neuroglia / ultrastructure
  • RNA, Messenger / metabolism
  • Rats
  • Receptor, IGF Type 2
  • Receptors, Cell Surface / analysis
  • Receptors, Cell Surface / genetics*
  • Receptors, Cell Surface / metabolism
  • Receptors, Somatomedin
  • Somatomedins / biosynthesis*


  • RNA, Messenger
  • Receptor, IGF Type 2
  • Receptors, Cell Surface
  • Receptors, Somatomedin
  • Somatomedins
  • Insulin-Like Growth Factor I
  • DNA