PEPTIDE TRANSPORTER FUNCTION AND PROLIDASE ACTIVITIES IN CACO-2 CELLS- A LACK OF COORDINATED EXPRESSION

Peptide transport and prolidase activities were measured to determine whether the expression of these two components of protein nutrition ar e coordinately regulated; i.e., whether an increase in the peptide tra nsporter function will necessarily lead to a higher prolidase activity , or vice versa. The results indicated that peptide transporter functi on and prolidase activity respond differently to cell differentiation and feeding schedules. The results also indicated that peptide transpo rt and prolidase activities were different in two Caco-2 cell ''clones '', with S-K cells transported peptides at higher rates but had lower total prolidase activities, when compared to ATCC cells. These results suggest that the expression of the peptide transporter function and p rolidase activity is not coordinated. In addition, both the transporte r and the prolidase activities affected the overall transport of Phe w hen given as the dipeptide Phe-Pro, supporting the notion that intesti nal absorption of peptides is an essential component of amino acid abs orption. In conclusion, the evidence suggests that the peptide transpo rter function and prolidase activity are not coordinately expressed by the human intestinal Caco-2 cells.