Interaction between glucocorticoids and epidermal growth factor in vitro in the growth of palatal mesenchymal cells from the human embryo.

Previous studies of ours have shown that palatal mesenchymal cells from the human embryo (HEPM cells) are responsive both to the glucocorticoid dexamethasone (DEX) and epidermal growth factor (EGF) through mechanisms associated with cytoplasmic and cell surface receptors, respectively. HEPM cell growth was inhibited by DEX and was stimulated by EGF. In the present study, the interactions between DEX and EGF were investigated. DEX (10(-6) M) enhanced EGF-stimulated HEPM cell growth as assessed by an increase in cell number and ornithine decarboxylase activity under serum-free cell culture conditions. DEX also enhanced the specific binding of 125I-EGF to these cells, which was reflected in an increase in both the number and the affinity of EGF receptors. EGF (1 ng/ml), on the other hand, decreased the number of sites per cell which specifically bind 3H-DEX. EGF completely prevented the inhibition by DEX of HEPM cell growth. These results indicated that DEX and EGF interact with each other in the process(es) regulating HEPM cell growth. This interaction may be partially influenced by direct modulation of existing receptors for DEX and EGF present in the cells.