Ussing chamber results for amino acid absorption of protein hydrolysates in porcine jejunum must be corrected for endogenous protein

BACKGROUND: Ussing chambers have been used extensively as an ex vivo model to investigate intestinal nutrient absorption. in this study Ussing chambers were used to investigate the absorption of amino acids and peptides in pig jejunal tissue using a highly hydrolysed casein hydrolysate (PeptoPro (R)), casein and whey protein isolate after they had been digested with pepsin and pancreatin to simulate digestion products in the jejunum. Jejunal tissue was collected from three pigs and mounted into Ussing chambers, equilibrated, and the luminal chamber loaded with one of three test nitrogen sources. Luminal solution samples were taken every 10 min over a 90 min incubation period and the amino acid concentration determined. To determine the endogenous amino acid contribution of the tissue to the luminal solution, Ussing chambers containing no test N source (blanks) were prepared and treated similarly to the Ussing chambers containing the test N sources. RESULTS: The endogenous amino acid contribution was 0.5 mg in the luminal solution at time 0 and increased to 1 mg after 90 min. The mean amino acid absorption after 10 min incubation for the pre-digested highly hydrolysed casein hydrolysate (116.6%) was significantly (P < 0.05) higher than for the pre-digested casein (7.6%) and whey protein isolate (6.7%). CONCLUSION: Endogenous amino acids were a quantitatively significant portion of the luminal solution amino acids present in the Ussing chambers containing the test N sources. Ussing chambers may be a suitable tool for studying amino acid absorption of protein hydrolysates but correction for the endogenous amino acid contribution from the intestinal tissue must be made. (C) 2009 Society of Chemical Industry