Carrier mediated transport of amino acids, small peptides, and their drug analogs

Abstract

The oral absorption of amino acids, small peptides and their analogs has been studied in rats using single pass intestinal perfusion. The experimental data was analyzed using a modified boundary layer method permitting the calculation of intrinsic membrane absorption parameters. Cefatrizine, l-Dopa, α-methyldopa, and l-PHE demonstrated concentration dependent absorption. Furthermore, the absorption of the amino acid analog, l-Dopa, was significantly inhibited by l-Leucine. Cefatrizine absorption was significantly inhibited by the peptide PHE-PHE (20 mM whereas the amino acid l-PHE (100 mM) did not inhibit its absorption. The results clearly demonstrate that l-Dopa and α-methyldopa oral absorption occurs via the amino acid pathway, while cefatrizine absorption occurs via the peptide pathway. These results indicate that nutrient pathways may function as a possible route for the oral delivery of selected drugs.