The action of epidermal growth factor on human amnion prostaglandin E2 output

The mechanism of stimulatory action of epidermal growth factor on term human amnion prostaglandin E2 production was studied. Monolayer cultures of amnion epithelial cells from spontaneous vaginal deliveries were preincubated for 24 h with serum-free media and treated with epidermal growth factor, calcium ionophore A23187 (4.5 microM), and arachidonate. Cumulative prostaglandin E2 output was not stimulated by epidermal growth factor (less than or equal to 200 ng/mL) or A23187 alone or the two added together. Pretreating the cells with epidermal growth factor for at least 2 h followed by A23187 or arachidonate (in the continuing presence of epidermal growth factor), however, stimulated prostaglandin E2 output up to 14-fold. The maximum effect of epidermal growth factor was attained at 1-10 ng/mL, while the EC50 was 0.2-0.32 ng/mL. Ionophore- or arachidonate-promoted prostaglandin E2 output was not stimulated by pretreatment with platelet-derived growth factor, fibroblast growth factor, and beta-transforming growth factor. Cycloheximide added before, at the same time as, or up to 30-60 min after epidermal growth factor completely abolished the stimulation. Epidermal growth factor did not affect [14C]arachidonate incorporation into cells or cell lipids. These results suggest that epidermal growth factor promotes, specifically and in a protein synthesis dependent manner, the conversion of arachidonate to prostaglandin E2. The provision of exogenous or endogenously liberated arachidonate is also necessary for enhanced amnion prostaglandin E2 production.