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      Epidermal Growth Factor Enhancement of Insulin-Like Growth Factor-I-Induced Down-Regulation of Insulin-Like Growth Factor I Receptor in Cultured Placental Trophoblastic Cells

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          Epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) synergistically stimulate placental lactogen (hPL) secretion by placental cells. To understand the mechanism of actions we have investigated a possible heterologous regulatory effect of EGF and IGF-I on each other’s receptors. Pretreatment of the cells with IGF-I had no effect on [<sup>125</sup>I]-EGF binding or the down-regulation of EGF receptor. Pretreatment of the cells with EGF, concomitantly with IGF-I, had no effect on [<sup>125</sup>I]-IGF-I binding but it augmented the IGF-I down-regulation of IGF-I receptor. The time required to initiate the IGF-I-induced down-regulation of IGF-I receptor was reduced by 4 h in the presence of EGF. IGF-I-down-regulated decreased (p < 0.05) receptor numbers were further decreased (p < 0.05) in the presence of EGF. These results suggested that the synergistic effect of EGF and IGF-I seen in hPL secretion by placental cells is not due to direct heterologous hormone-receptor interactive effects. However, the effects seen may be due to a differentiating effect of EGF sensitizing the cells for responsiveness to IGF-I.

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          Author and article information

          Horm Res Paediatr
          Hormone Research in Paediatrics
          S. Karger AG
          02 December 2008
          : 35
          : 6
          : 246-251
          Department of Medicine, University of Saskatchewan, Saskatoon, Sask., Canada
          181914 Horm Res 1991;35:246–251
          © 1991 S. Karger AG, Basel

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          Pages: 6
          Original Paper


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