Effects of concentration on in vivo absorption of a peptide containing protein hydrolysate

Amino acid absorption from a peptide-containing protein hydrolysate and an equivalent amino acid mixture over a range of concentrations of the two--such as is thought to be found in the normal intestine after a meal--has been studied using a jejunal perfusion technique in man. The relative rates of amino acid absorption from the protein hydrolysate and amino acid mixture varied markedly with concentration, demonstrating that the global hypothesis that peptides confer an advantage in amino acid absorption in vivo is too simple. There is a highly significant correlation between amino acid absorption and the concentrations of amino acid in the perfusate, whether this contained amino acid or protein hydrolysate, suggesting that, under these experimental conditions at least, the presence of distinct amino acid and peptide transport systems is relatively unimportant. Doubt is thus cast upon suggestions derived from previous intestinal perfusion experiments that intact peptide transport may be nutritionally significant in man.