Improvement of L-dopa absorption by dipeptidyl derivation, utilizing peptide transporter PepT1

In the present study, possible enhancement of intestinal absorption of L-do pa by utilizing intestinal peptide transporter was examined using Caco-2 ce lls and Xenopus oocytes expressing human peptide transporter (hPepT1). To s ee whether this peptide transporter could be utilized for the improvement o f L-dopa absorption, we employed a dipeptide-mimetic derivative of L-dopa, L-dopa-L-Phe. L-Dopa-L-Phe inhibited the uptake of [C-14]Gly-Sar, but not t hat of L-[H-3]dopa by Caco-2 cells. Uptake of L-dopa-L-Phe was increased by expression of hPepT1 in Xenopus oocytes. The appearance of L-dopa and its metabolite, dopamine, on the basolateral side of Caco-2 cells was significa ntly higher after addition of L-dopa-L-Phe than after that of L-dopa and wa s reduced by the presence of Gly-Sar on the apical side. These results indi cate that the L-dopa-L-Phe is absorbed more efficiently than L-dopa and is taken up via the peptide transporter, but not via the amino acid transporte r, demonstrating the possibility of targeting the peptide transporter as a means for improving intestinal absorption of peptide-like drugs.