Profound increase in viscosity and aggregation of pig gastric mucin at low pH.

Published

Journal Article

Epithelial mucins are glycoproteins of very large molecular weight that provide viscoelastic and gel-forming properties to mucus, the jellylike protective layer covering epithelial organs. In the mammalian stomach the mucus gel layer protects the underlying epithelial cells from HCl in the lumen. We report here that pig gastric mucin undergoes a 100-fold increase in viscosity in vitro when pH is lowered from 7 to 2. Sedimentation velocity and dynamic light-scattering measurements revealed the formation of extremely large aggregates at low pH consistent with the observed increase in viscosity. Aggregation of mucin at low pH was prevented by increasing the ionic strength, suggesting the involvement of electrostatic interactions. Trypsin digestion and thiol reduction, but not enzymatic removal of neuraminic acid, prevented aggregation at low pH. This implies that the peptide core rather than the oligosaccharide side chains of the molecule is involved in the aggregation of mucin at low pH. Increased aggregation and viscosity at low pH were also observed in a solvent made to mimic the ionic composition of gastric juice, indicating the physiological relevance of our findings. Our observations suggest that one mechanism of gastric protection may be the ability of gastric mucin to undergo aggregation with a marked increase in viscosity at low pH.

Full Text

Duke Authors

Cited Authors

  • Bhaskar, KR; Gong, DH; Bansil, R; Pajevic, S; Hamilton, JA; Turner, BS; LaMont, JT

Published Date

  • November 1991

Published In

Volume / Issue

  • 261 / 5 Pt 1

Start / End Page

  • G827 - G832

PubMed ID

  • 1719823

Pubmed Central ID

  • 1719823

Electronic International Standard Serial Number (EISSN)

  • 2163-5773

International Standard Serial Number (ISSN)

  • 0002-9513

Digital Object Identifier (DOI)

  • 10.1152/ajpgi.1991.261.5.g827

Language

  • eng