2,3,7,8-tetrachlorodibenzo-p- dioxin reduces high-affinity binding of epidermal growth factor to cell surface receptors in C3H 10T1/2 cells

The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on epidermal growth factor (EGF)-binding characteristics was studied in a cultured embryonic fibroblast cell line, C3H 10T1/2. At very low concentrations, TCDD was found to cause a persistent decline in EFG binding, the median effective concentration (EC-50) being 10^?12M. This particular effect was most conspicuous when TCDD was added at the time of medium change with fresh Dulbecco's modified Eagle's medium. Cells at an early stage of confluency were more responsive to TCDD than those at a later stage. Although most reported TCDD-evoked biological changes are recognized to occur slowly during the course of a few days to weeks, the response of C3H 10T1/2 cells to TCDD was swift, showing a sign of decline of EGF binding as early as three hours after TCDD addition. C3H 10T1/2 cells appear to be an excellent in vitro model to study TCDD's biochemical action mechanisms.