INCREASED INVITRO INTESTINAL PERMEABILITY IN SUCKLING RATS EXPOSED TOCOW MILK DURING LACTATION

Specific mucosal barrier functions of the gut develop in the newborn t o combat the constant challenge of foreign antigens. To determine whet her exposure to cow milk antigens interferes with this maturational pr ocess, jejunal permeability to macromolecules and the activation of im mune mechanisms were studied in preweaning rats. At the age of 14 days , rat pups were divided into three feeding groups. Controls (n = 18) r emained on normal matemal milk; group CM (n = 27) additionally receive d a daily gavage feed of cow milk; and in group D (n = 23), cow milk w as given to dams. At 21 days, when ''gut closure'' normally occurs, in testinal in vitro absorption of horseradish peroxidase in its intact f orm was significantly higher in group CM and in group D than in contro ls (F = 5.6; p = 0.006): group CM: mean, 37.8 ng/h/cm2; 95% confidence interval (CI), 19.4-73.6; group D: mean, 26.9 ng/h/cm2; 95% Cl, 8.2-8 8.2; controls: mean, 4.0 ng/h/cm2; 95% Cl, 1.2-13.9. In association wi th increased jejunal permeability, there was enhanced jejunal eosinoph ilic infiltration in group CM. In group D, the number of specific anti body-secreting cells in peripheral blood against beta-lactoglobulin wa s significantly higher than in group CM and controls. These data indic ate that there is a critical period in development when feeding cow mi lk antigens delays gut closure. They further suggest that mucosal barr ier function is impaired due to a local hypersensitivity reaction to c ow milk antigens, irrespective of the protection of maternal milk or m atemal antigen processing.