Carrier Mediated Transport of Amino Acids, Their Drug Analogs*

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, cu-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 a-methyldopa oral absorption occurs via the amino acidpathway, 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.