[The experimental study of epidermal growth factor -effects of epidermal growth factor on the cyclic nucleotide...

Incubation of pig skin slices with epidermal growth factor (EGF) caused an increase in intracellular cyclic GMP concentration of pig epidermis. A significant increase was found after 1 hr of incubation and reached a peak by 6 hrs. EGF caused no change in the cyclic AMP level, nor did it affect epinephrine-induced cyclic AMP responses. EGF also stimulated protein phosphorylation in pig epidermis. The stimulation was both time and dose dependent, and was not inhibited by the simultaneous addition of cycloheximide. The addition of cyclic GMP did not mimic the EGF treatment and EGF stimulated protein phosphorylation in 20 minutes. Phosphoproteins stimulated by EGF were identified by SDS-PAGE and autoradiographic analysis. The identified phosphoproteins were fibrous keratin proteins (MW. 65,000, 60,000, 56,000 and 51,000) and soluble protein (MW. 30,000). Calcium ion potentiated the phosphorylation of keratin proteins by EGF. Ionophore A23187 plus calcium ion also enhanced the phosphorylation of keratin proteins.