Studies on the uptake of dipeptides in brush border membrane vesicle from rat intestine

Four dipeptides, namely D-phenylglycine-L-alanine (1a), D-phenylglycine-L-lysine (1b), D-phenylglycine-L-serine (1c), and D-p-hydroxyphenylglycine-L-serine (1d) were synthesized. The intestinal absorption of these dipeptides was conducted on an in vitro uptake experiment in brush-border membrane vesicle (BBMV) prepared trom isolated rat intestine. Compounds 1a and 1d showed fast initial uptake at pH(o) = 5.5/pH(i) = 7.4, indicating that the H⁺-coupled dipeptide-mediated carrier transport system was involved in the absorption of the dipeptides. The amphoteric structure was essential for the uptake of 1a, but not for 1d. The structural requirement of this transport system for its substrate seemed to be rigid and diversified among the dipeptides tested. On the other hand, compound 1b, the lysine analogue of 1a, showed fast initial uptake at pH(o) = 7.4/pH(i) = 7.4, indicating the involvement of a neutral pH-preferring transport system in the uptake of this compound.