Somatomedin C/insulin-like growth factor I binding and action in human fibroblasts aged in culture: Impaired synergism with dexamethasone

C. A. Conover, R. G. Rosenfeld, R. L. Hintz

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Somatomedin C/insulin-like growth factor I (SM-C/IGF-I) binding and action were compared in human fibroblasts serially passaged in vitro. Binding of [125I]SM-C/IGF-I was identical in early and late passage cells, with 50% displacement at 4 ng/ml SM-C/IGF-I. Maximal concentrations of SM-C/IGF-I (100 ng/ml) stimulated [3H]thymidine incorporation equally in both early and late passage cells. Furthermore, dose response curves indicated that there was no alteration in the sensitivity of cells to SM-C/IGF-I with age. Preincubation with dexamethasone (10-7 M) potentiated SM-C/IGF-I's mitogenic effect in early passage cells. In contrast, dexamethasone had no effect on SM-C/IGF-I stimulation of [3H]thymidine incorporation or replication of late passage cells. These data indicate that fibroblasts passaged in vitro have normal SM-C/IGF-I binding and are capable of responding to the mitogenic effect of SM-C/IGF-I. The synergism between SM-C/IGF-I and dexamethasone in stimulating DNA synthesis and replication of early passage fibroblasts is lost, however, in late passage cells.

Original languageEnglish (US)
Pages (from-to)308-314
Number of pages7
JournalJournals of Gerontology
Issue number3
StatePublished - Jan 1 1987


ASJC Scopus subject areas

  • Aging

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