Characterization of insulin-like growth factor I receptors on cultured rat bone cells: Regulation of receptor concentration by glucocorticoids

Ann Bennett, Theresa Chen, David Feldman, Raymond L. Hintz, Ron G. Rosenfeld

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Abstract

A specific receptor for insulin-like growth factor I (IGF-I) has been demonstrated in cultured fetal rat osteoblastlike bone cells. Specific binding of [125I]IGF-I to bone cells incubated at 15 C reached a steady state by 5 h. Half-maximal inhibition of [125I]IGF-I binding by unlabeled IGF-I was observed at 7 ng/ml. Multiplication-stimulating activity, insulin, and proinsulin were less effective than unlabeled IGF-I in competing for receptor occupancy. Scatchard analysis showed a curvilinear plot, with a Ka similar to that observed in human fibroblasts. Incubation of cell monolayers with glucocorticoids resulted in a concentration-dependent increase in [125I]IGF-I binding. This increase in [125I]IGF-I binding was dependent on cell density. After a 2-day exposure to dexamethasone, no increase in binding was observed in sparsely plated cells; however, an increase in binding was observed after 3 days in culture (log phase) and was maximal by 5 days (peak log phase). These data indicate that rat bone cells possess a specific receptor for IGF-I with binding characteristics similar to those reported in human fibroblasts, and that IGF-I receptor concentrations are increased by exposure to glucocorticoids. A role for glucocorticoids and IGF-I in rat bone proliferation is suggested by these findings.

Original languageEnglish (US)
Pages (from-to)1577-1583
Number of pages7
JournalEndocrinology
Volume115
Issue number4
DOIs
StatePublished - Jan 1 1984

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ASJC Scopus subject areas

  • Endocrinology

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