Transport of bovine milk-derived opioid peptides across a Caco-2 monolayer

Abstract The transepithelial transport of μ-opioid (MOP) receptor agonists, i.e., bovine β-casomorphin-5 and -7 (derived from β-casein) and an antagonist, i.e., casoxin-6 (derived from κ-casein) were investigated using a human intestinal cell (Caco-2) monolayer. To determine the transport pathway of the peptides across Caco-2 monolayers, two directions of the transport (apical-to-basolateral and basolateral-to-apical) were studied. All investigated peptides were transported across Caco-2. The cumulative fractions of transported peptides were increased linearly in time in each case. The permeability coefficients ( P aap ) calculated for all peptides in two transport directions ranged between 0.57 and 9.21 × 10 −6  cm min −1 . These data suggest the possibility of transport of opioid peptides derived from food across human intestinal mucosa.