Epidermal growth factor (EGF) plays an important role in the development of the neonatal intestinal tract and affects the integrity of adult stomach. This study examined the effects of EGF on the development of mucosal responses to luminal H+ in rats of various ages. Mucosal response to luminal acid (300 mN) was measured in rats between 10 and 60 days after birth. Permeability changes were expressed as H+ loss and Na+, K+, and protein appearance in the luminal instillate. Losses of H+ and luminal appearances of Na+, K+, and protein were greater in animals older than 20 days of age compared with younger rats. Mucosal permeability responses to 300 mN HCl were reduced by enteral or parenteral treatment with EGF (5-50 or 10-100 micrograms/kg sc) in rats 20 days of age and older. EGF did not consistently affect ion and protein fluxes in 10- and 15-day-old rats treated with HCl. Likewise EGF did not stimulate gastric HCO3- secretion in any of the age groups examined. Injection of 8-day-old rats with corticosterone acetate (250 mg/kg) did not affect ion or protein fluxes in EGF-treated 10-day-old rats. However steroid treatment did result in a reduction in Na+ and K+ fluxes in 15-day-old rats receiving EGF. EGF was detected in salivary and duodenal tissue of rats and in the maternal milk of rat dams.(ABSTRACT TRUNCATED AT 250 WORDS)