Development and adaptation of protein digestion
Austic, R.E.
Journal of Nutrition 115(5): 686-697
1985
ISSN/ISBN: 0022-3166 PMID: 3889240 Document Number: 258007
Protein digestion is a complex process in which most aspects have a developmental pattern of activity. Gastric pH and intestinal peptide and amino acid transport as well as the activities of pepsinogen, trypsin, chymotrypsin, enterokinase and intestinal dipeptidases vary during development. No one species had been assessed for all these aspects and it is not possible to present an integrated development view of protein digestion. The following developmental changes, however, have been observed. Gastric pH declines, and peptic and pancreatic proteases exhibit increasing activity in pigs and rats after birth. The increase in pigs is gradual over several weeks starting at birth, whereas the increases in the rat begin at 2 weeks, just before the time of weaning. The activities of dipeptidases in the rat and pig, peptide transport systems in the guineapig and rabbit and amino acid transport systems in the rat, rabbit, guineapig and chicken, however, appear (with few exceptions) to be active in the small intestine at the time of birth. Frequently, these activities peak in the neonate and decline during the postnatal period. In the rat, dietary protein tends to increase the activities of proteases and intestinal peptidases and to increase the rate of uptake of amino acids by the intestinal epithelium. Individual dietary amino acids also influence amino acid transport systems. The results indicate that most processes in protein digestion undergo marked changes during prenatal and postnatal development and are influenced by the level of feeding and composition of the diet.