Effects of peptides derived from dietary proteins on mucus secretion in rat jejunum

Am J Physiol Gastrointest Liver Physiol. 2002 Sep;283(3):G521-8. doi: 10.1152/ajpgi.00535.2001.


The hypothesis that dietary proteins or their hydrolysates may regulate intestinal mucin discharge was investigated in the isolated vascularly perfused rat jejunum using an enzyme-linked immunosorbent assay for rat intestinal mucins. On luminal administration, casein hydrolysate [0.05-5% (wt/vol)] stimulated mucin secretion in rat jejunum (maximal response at 417% of controls). Lactalbumin hydrolysate (5%) also evoked mucin discharge. In contrast, casein, and a mixture of amino acids was without effect. Chicken egg albumin and its hydrolysate or meat hydrolysate also did not modify mucin release. Interestingly, casein hydrolysate-induced mucin secretion was abolished by intra-arterial TTX or naloxone (an opioid antagonist). beta-Casomorphin-7, an opioid peptide released from beta-casein on milk ingestion, induced a strong mucin secretion (response at 563% of controls) that was inhibited by naloxone. Intra-arterial beta-casomorphin-7 also markedly increased mucin secretion (410% of controls). In conclusion, two enzymatic milk protein hydrolysates (casein and lactalbumin hydrolysates) and beta-casomorphin-7, specifically, induced mucin release in rat jejunum. The casein hydrolysate-induced mucin secretion is triggered by a neural pathway and mediated by opioid receptor activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Caseins / pharmacology
  • Dietary Proteins / metabolism
  • Dietary Proteins / pharmacology*
  • Endorphins / pharmacology
  • Hydrolysis
  • In Vitro Techniques
  • Jejunum / drug effects*
  • Jejunum / metabolism*
  • Male
  • Mucus / metabolism*
  • Peptide Fragments / pharmacology
  • Protein Hydrolysates / pharmacology
  • Rats
  • Rats, Wistar


  • Caseins
  • Dietary Proteins
  • Endorphins
  • Peptide Fragments
  • Protein Hydrolysates
  • trypticase-soy broth
  • beta-casomorphin 7