['Copper deficiency could cause fatal hematological and neurological disorders or other diseases. Amino acids are involved in the absorption of copper ions. The purpose of this study is to evaluate the absorption of copper in amino acid complex forms and determine its mechanism in the Caco-2 cell culture model.', 'The human colonic adenocarcinoma cell line Caco-2 culture model was used to determine the permeability of copper ions in inorganic form (CuSO4) and the amino acid complex forms. Lysine and methionine, as well as carboplatin were used to determine the possible involvement of amino acid transporters or copper transporter 1 (CTR1).', 'The results showed that all of the amino acid complex forms facilitated copper absorption. The apparent permeabilities of copper ions in these complex forms were at least 7.6 fold higher than those in the CuSO4 form. The permeability rank order of copper in various amino acid complex forms was Cu-glutamate<Cu-lysine=Cu-aspartic acid=Cu methionine<Cu-arginine<Cu-(lysine/glutamate). Mechanistic studies revealed that the enhanced absorption of copper in copper amino acid complexes could be the result of enhanced uptake (as in Cu-methionine complex) or enhanced basolateral efflux (as in Cu-lysine complex). Copper transporter 1 (or CTR1) inhibitor carboplatin did not affect the absorption of copper in Cu-methionine complex, suggesting that the dominant pathway for copper amino acid complexes is not CTR1.'] Does amino acid facilitate absorption of copper in the Caco-2 cell culture model?