Handling of gliadin peptides B1-B4 and of cow's milk proteins by rat jejunum gut sacs.

The rat everted gut sac was used as a model of intestinal protein and peptide handling to study small intestinal binding and uptake of different gliadin peptide fractions (B1, B2, B3, B4) in comparison with bovine serum albumin (BSA), alpha-lactalbumin (alpha-LA), and a BSA peptide fraction (BSA-P). Not only binding curves, but also uptake curves of BSA, alpha-LA, and BSA-P were run in parallel between 1 and 30 min. Binding and uptake obviously depended on molecular weight. BSA-P binding was found to be highest of all. Binding of BSA was significantly lower. After 20 and 30 min, significantly more alpha-LA and BSA-P were taken up than was BSA. There was no difference in handling of the gliadin peptide fractions tested by the gut mucosal surface. Binding of B1-B4 was significantly higher than binding of BSA and was significantly lower than binding of BSA-P. No difference was found between binding of B1-B4 and alpha-LA. There was a consistently higher uptake of all gliadin peptide fractions, independent of molecular weight. Slopes for uptake curves of B1-B4 were steeper than those of BSA, alpha-LA, and BSA-P. Crossing of uptake over binding curves was consistently observed with gliadin fractions, but never with cow's milk proteins/peptides. Differences in uptake between gliadin peptide fractions and cow's milk proteins/peptides might be based on a specific interaction between gliadin peptides and the gut surface.