Increased in vitro intestinal permeability in suckling rats exposed to cow milk during lactation

Abstract

Specific mucosal barrier functions of the gut develop in the newborn to combat the constant challenge of foreign antigens. To determine whether exposure to cow milk antigens interferes with this maturational process, jejunal permeability to macromolecules and the activation of immune mechanisms were studied in preweaning rats. At the age of 14 days, rat pups were divided into three feeding groups. Controls (n = 18) remained on normal maternal milk; group CM (n = 27) additionally received a daily gavage feed of cow milk; and in group D (n = 23), cow milk was given to dams. At 21 days, when "gut closure" normally occurs, intestinal in vitro absorption of horseradish peroxidase in its intact form was significantly higher in group CM and in group D than in controls (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% CI, 8.2-88.2; controls: mean, 4.0 ng/h/cm2; 95% CI, 1.2-13.9. In association with increased jejunal permeability, there was enhanced jejunal eosinophilic infiltration in group CM. In group D, the number of specific antibody-secreting cells in peripheral blood against beta-lactoglobulin was significantly higher than in group CM and controls. These data indicate that there is a critical period in development when feeding cow milk antigens delays gut closure. They further suggest that mucosal barrier function is impaired due to a local hypersensitivity reaction to cow milk antigens, irrespective of the protection of maternal milk or maternal antigen processing.