Insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-IR) immunoreactivity in normal and osteopetrotic (toothless, tl/tl) rat tibia

B K Joseph, S C Marks, D A Hume, M J Waters, A L Symons

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Insulin-like growth factor-I (IGF-I) plays a major role in regulating cell growth. This study examined the immunohistochemical distribution of IGF-I and IGF-I receptor (IGF-IR) in tibias from normal and osteopetrotic (toothless, tl/tl) rats, following treatment with colony stimulating factor-1 (CSF-1). In normal rats, immunoreactivity for IGF-I and IGF-IR was detected in cells of the articular and epiphyseal cartilage, secondary ossification centres, zones of resting and proliferating chondrocytes and bone marrow. Bone marrow cells immunoreactive for IGF-I and IGF-IR were significantly reduced in the tl/tl rat (p <0.001) compared with normal animals. Treatment of tl/tl rats with CSF-1 increased immunoreactivity for IGF-I and IGF-IR in bone marrow cells as well as the number of TRAP positive osteoclasts. This increase was the result of recruitment of a range of hematopoietic cell types, including eosinophils, polymorphs and a substantial number of monocyte-like cells demonstrating strong immunoreactivity to IGF-I/IGF-IR. The differences in relative immunoreactivity for IGF-I/IGF-IR by bone marrow cells in untreated and CSF-1-treated tl/tl rats indicate a CSF-1-dependent recruitment of cells bearing surface IGF-IRs which may be mediated by an increase in local or systemic IGF-I.
Original languageEnglish
Pages (from-to)279-91
Number of pages13
JournalGrowth Factors
Issue number4
Publication statusPublished - 1999


  • Acid Phosphatase
  • Animals
  • Biological Markers
  • Bone Marrow Cells
  • Cartilage, Articular
  • Immunohistochemistry
  • Insulin-Like Growth Factor I
  • Isoenzymes
  • Macrophage Colony-Stimulating Factor
  • Monocytes
  • Osteoclasts
  • Osteopetrosis
  • Rats
  • Rats, Mutant Strains
  • Receptor, IGF Type 1
  • Tibia


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