Serum glucocorticoids have persistent and controlling effects on insulinlike growth factor i action under serum-free assay conditions in cultured human fibroblasts |
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Authors: | Cheryl A Conover Ron G Rosenfeld Raymond L Hintz |
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Institution: | (1) Department of Pediatrics, Stanford University, 94305 Stanford, California |
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Abstract: | Summary The biological actions of insulinlike growth factor I (IGF-I) measured under serum-free assay conditions were found to be
significantly influenced by prior subculture conditions for adult human fibroblasts. Glucocorticoids seemed to be the major
medium variable affecting IGF-I action. IGF-I added to serum-free cultures had little or no effect on 14C]aminoisobutyric acid uptake or 3H]thymidine incorporation in human fibroblasts previously maintained in media containing serum with low glucocorticoid levels
or in serum stripped of endogenous steroids. However, a 48-h preincubation with dexamethasone resulted in a marked synergistic
increase in IGF-I stimulation of 14C]aminoisobutyric acid uptake and 3Hthymidine incorporation in these cultures. In contrast, IGF-I in serum-free medium seemed to be a potent mitogenic and metabolic
stimulus for human fibroblasts which had been subcultured in media with a high glucocorticoid content, either endogenous,
or supplemented. After these culture conditions, a 48-h preexposure to dexamethasone had no further enhancing effect on IGF-I
action. Dexamethasone also potentiated IGF-I, insulin, and epidermal growth factor stimulation of fibroblast replication depending
on the earlier subcultivation conditions. Thus, glucocorticoids are important modulators of IGF-I bioactivity in cultured
human fibroblasts. Serum glucocorticoids can exert a profound influence on the biological phenomena measured in cell culture,
even when the serum has been removed before the actual experiment, and must be carefully taken into account for accurate evaluation
of the biological function of IGF-I and other growth factors.
This work was supported in part by grants DK28229, DK36054, CA42106, RCDA01275, and DK24085 from the National Institutes of
Health, Bethesda, MD. |
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Keywords: | insulinlike growth factor I glucocorticoids dexamethasone serum human fibroblasts growth regulation |
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