A rapid and inexpensive method to assay transport of short chain peptides across intestinal brush-border membrane vesicles from the European eel (Anguilla anguilla)

Membrane potential depolarization due to electrogenic peptide transport activity was examined in eel (Anguilla anguilla) intestinal brush-border membrane vesicles (BBMV) by monitoring the fluorescence quenching of the voltage-sensitive dye 3,3'-diethylthiadicarbocyanine iodide. Our experimental approach consisted of generating an internal negative membrane potential mimicking in vivo conditions and measuring membrane potential depolarization due to different extravesicular dipeptides. Peptide-dependent membrane potential depolarization was observed in both the presence and absence of extravesicular Na+ and was inhibited by diethylpyrocarbonate, which is consistent with the involvement of electrogenic, Na+-independent, H+-dependent peptide transport activity. Kinetic analysis indicated that peptide-dependent membrane potential depolarization is a saturable process (K-m,K-app similar to 1.5 mmol L-1) and that within the 0.1-10 mmol L-1 peptide range a single carrier system is involved in the transport process. Our results suggest that a peptide transport activity, kinetically resembling the PepT1(Slc15A1)-type-mediated H+/peptide cotransport action, can be monitored in eel intestinal BBMV using an easy and inexpensive fluorescence assay.