The role of surface and intracellular mucus in gastric mucosal protection against hydrogen ion. Compositional differences.

The role of surface and intracellular mucus in gastric mucosal protection against hydrogen ion was investigated. Gastric mucosa, prepared from dog and rat stomachs at various stages of mucus depletion, was mounted in the permeability chamber, and the diffusion of hydrogen ion from the luminal to the serosal side was measured. Removal of the surface mucus caused a 42.9% increase in the permeability of rat gastric mucosa and a 47.4% increase in the permeability of dog gastric mucosa. The permeability to hydrogen ion of gastric mucosa depleted of its surface and intracellular mucus increased 216% in the case of the dog and 280% with the rat. Compositional analysis showed that in both animals the intracellular mucus had a higher content of lipids, covalently bound fatty acids, and carbohydrates, whereas the protein content was higher in the surface mucus. The results suggest that, although both the surface and intracellular mucus participate in the retardation of hydrogen ion diffusion, the contribution of the latter appears to be greater.