Abstract
Replicative DNA synthesis, as measured by thymidine incorporation, has been measured in rat uterine cells in primary culture in response to growth factors. Insulin, insulin-like growth factor-I (IGF-I), multiplication-stimulating activity (MSA) and platelet-derived growth factor (PDGF) stimulated DNA synthesis, while estradiol, epidermal growth factor (EGF), transforming growth factor-beta (TGF-beta), basic fibroblast growth factor (bFGF) and relaxin did not stimulate or did so weakly and only at very high concentrations. Uterine acid extracts also stimulated DNA synthesis. IGF-I stimulated at concentrations consistent with its acting through the IGF-I receptor; however, insulin stimulated at concentrations higher than expected for its acting through its receptor and this its action may be mediated through the IGF-I receptor. IGF-I was found in uterine tissue by radioimmunoassay (RIA). There was a 5- to 10-fold increase in IGF-I in the uteri from ovariectomized rats that had been treated with estradiol 24 h earlier. This is analogous to the increase in growth factor activity found previously in rat uterus after 24-h estradiol treatment (Beck, C.A. and Garner, C.W. (1989) Mol. Cell. Endocrinol. 63, 93-101). These data are consistent with the hypothesis that estradiol effects in the uterus are in part mediated through IGF-I.
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