Intestinal transport of the lactokinin Ala-Leu-Pro-Met-His-Ile-Arg through a Caco-2 Bbe monolayer

ACE inhibitory peptides are biologically active peptides that play a role in blood pressure regulation. When derived from food proteins during food processing or gastrointestinal digestion, these peptides could function as efficient agents in treating and preventing hypertension. However, in order to exert an antihypertensive effect by inhibition of the ACE enzyme, they have to reach the bloodstream intact. The aim of this research was to assess if the known ACE inhibitory peptide Ala-Leu-Pro-Met-His-Ile-Arg, derived from a tryptic digest of β-lactoglobulin, could be absorbed through a Caco-2 Bbe cell monolayer in an Ussing chamber and reach the serosal side undegraded. Samples of the mucosal compartment showed high ACE inhibitory activity. No or only little ACE inhibitory activity was detected in the serosal compartment. However, when the serosal sample was concentrated three-fold, a substantial ACE inhibitory activity was registered. Concomitantly, HPLC and MS clearly showed the presence of Ala-Leu-Pro-Met-His-Ile-Arg in the mucosal compartment, whereas in the serosal compartment only MS was able to detect the heptapeptide. In conclusion, under the observed experimental conditions, the ACE inhibitory peptide Ala-Leu-Pro-Met-His-Ile-Arg was transported intact through the Caco-2 Bbe monolayer, but in concentrations too low to exert an ACE inhibitory activity.