Background: Lactobacilli constitute a major part of the microflora throughout the gastrointestinal tract. This study aimed to investigate the effect of lactobacilli on the gut mucosal barrier.
Methods: Rat pups were divided into three experimental feeding groups at the age of 14 days. In addition to normal maternal milk, group "milk" received a daily gavage of cow milk, group "milk-GG" received Lactobacillus casei strain GG with cow milk, and controls were gavaged with the same volume of water. At 21 days, the absorption of horseradish peroxidase across patch-free jejunal segments and segments containing Peyer's patches was studied in Ussing chambers.
Results: The mean absorption of intact horseradish peroxidase expressed in ng.h-1.cm-2, was significantly different in the study groups in both patch-free segments (controls, 9 [95% confidence interval, 7-12]; milk, 72 [60-87]; and milk-GG, 15 [4-52]) and in segments containing Peyer's patches (controls, 3 [1-17]; milk, 80 [43-151]; and milk-GG, 15 [4-56]). There was a significant increase in the frequency of cells secreting antibodies to beta-lactoglobulin (enzyme-linked immunospot assay) in the milk-GG group.
Conclusions: Prolonged cow milk challenge in suckling rats increases gut permeability to intact proteins, whereas Lactobacillus GG counteracts this permeability disorder. The results suggest a link between the intensity of the antigen-specific immune response and stabilization of the mucosal barrier.