Transport properties of bovine and reindeer β-lactoglobulin in the Caco-2 cell model

β-Lactoglobulin (βLG) is a protein that binds ligands like fatty acids and retinol into the hydrophobic pocket. Our purpose was to study bovine and reindeer βLG as transporter molecules and compare their transport properties across Caco-2 cell membrane. The reindeer βLG has more valuable binder characteristics than bovine βLG because it has only one genetic phenotype and it seems to exhibit better immunological properties. The permeation of βLG in Caco-2 cells was evaluated by immunoblotting, and the permeation of the model substances retinol, palmitic acid and cholesterol with and without βLG was determined using [3H]-labelled ligands. Both bovine and reindeer βLG were able to pass across a Caco-2 cell monolayer similarly. Unbound and βLG-bound [3H]retinol and [3H]palmitic acid were equally transported across the Caco-2 cell layer, whereas [3H]cholesterol could not pass across Caco-2 cells with or without βLG at any of the studied circumstances. Thus, the bovine and reindeer milk βLG is not a suitable protein to enhance transport of ligands across the Caco-2 cell membrane, used for predicting intestinal absorption.