Epidermal growth factor (EGF) originating from salivary glands has been shown to affect the development and integrity of rodent gastrointestinal mucosa. Because newborn rats receive EGF from maternal milk, we have examined the effect of sialoadenectomy as a method of depleting EGF in milk on the resistance of neonatal rat mucosa to luminal H+. Rat dams were sialoadenectomized (SALX) or sham operated 5 days after parturition. Experiments were performed on newborns 10-22 days old. Mucosal permeability responses to intraluminal HCl (300 mM) were examined in terms of luminal appearances of Na+, K+, and protein and H+ loss. EGF levels in maternal milk were determined by immunoassay. In rat pups from control litters, luminal HCl resulted in an age-associated increase in cation and protein flux across the gastric mucosa. Luminal cation and protein fluxes observed in 10- to 18-day-old rat pups from SALX dams were not significantly different from similarly aged rats from control dams. However, in 19- to 22-day-old rats from SALX dams, the permeability responses to luminal HCl were exacerbated compared with similarly aged neonates from control dams. These responses were reduced by treatment with EGF. EGF levels in milk from sham-operated and SALX dams were not significantly different in the 10- to 16-day lactational period. However, in SALX dams EGF was significantly reduced at 19 and 22 days. Chromatographic elution pattern of milk EGF was dissimilar to the pattern exhibited by submandibular gland EGF.(ABSTRACT TRUNCATED AT 250 WORDS)