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Protein digestion and absorption in human small intestine



Protein digestion and absorption in human small intestine



Gastroenterology 76(6): 1415-1421



The extent of digestion and absorption of bovine serum albumin (BSA) of a mixed meal was quantitatively examined in 6 healthy volunteers by means of 5-lumen intestinal tube with perfused segments in the proximal jejunum and terminal ileum and a nonperfused sampling site in the proximal ileum. At all times throughout the 4 h postprandial test periods, the ratio of protein to the polyethylene glycol (PEG) meal marker in the proximal jejunal samples was .apprx. 40% of protein to PEG ratio of the meal, indicating digestion and/or absorption of 60% of meal protein at this level. In the terminal ileum, the protein to PEG ratio was less than 1% of the original meal. About 0.5 g of protein passed through the terminal ileum during the test period. A protein band electrophoretically coincident with BSA on sodium dodecyl sulfate-polyacrylamide gels was detected in samples from the proximal jejunum and proximal ileum throughout the study, but was not found in the terminal ileal samples. The ratio of amino acids to oligopeptides was constant throughout the small intestine. About 200 mg of free amino acid or oligopeptide N passed into the colon during the 4 h after the meal ingestion. Trypsin concentration was similar in jejunum and proximal ileum. When corrected for reduction of intraluminal volume in the terminal ileum, it was 8% of activity in the proximal jejunum. Quantitative digestion and absorption of a protein, BSA, is apparently complete by the time an ingested meal has traversed the total small intestine, and that the ileum is important for the completion of the process.

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Accession: 000728221

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PMID: 437440



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