Ultrastructure of the hydrophobic gastric surfactant barrier in the dog.
OBJECTIVE
To confirm the hydrophobicity of the luminal surface of the canine stomach and to elucidate the ultrastructure of the lining imparting that property.


METHODS
Gastric and duodenal mucosal samples from eight dogs were collected immediately after euthanasia and subjected to contact angle measurement using a goniometer. Other samples were examined by electron microscopy following a fixation procedure known to preserve phospholipids and oligolamellar structures.


RESULTS
Contact angles for the canine gastric mucosal surface (85.1 +/- 5.5) were significantly greater (P < 0.0001) than for the duodenum (24.0 +/- 1.7). Electron microscopy revealed the existence of surfactant as abundant osmiophilic phospholipid material within the gastric and duodenal mucosae.


CONCLUSIONS
We have confirmed the hydrophobic nature of the canine gastric mucosa whereas the luminal surface of the duodenum is hydrophilic. We propose that the water-repellent nature of the canine gastric lining contributes to the 'gastric mucosal barrier' and is imparted by an oligolamellar layer of surface-active phospholipid ('gastric surfactant') adsorbed to the surface. Both gastric and duodenal mucosae may also utilise phospholipids as an intercellular defense mechanism in the event that tight junctions are breached by acid. It is tempting to speculate that a deficiency of gastric phospholipids may predispose dogs to ulcers. Further, exogenous administration of phospholipids may be useful in preventing gastric ulceration.
D000818:Animals; D004285:Dogs / Q000033:anatomy & histology*; D005260:Female; D005753:Gastric Mucosa / Q000648:ultrastructure*; D007413:Intestinal Mucosa / Q000648:ultrastructure*; D008297:Male; D012016:Reference Values; D013499:Surface Properties; D013501:Surface-Active Agents / Q000032:analysis*; D016707:Tissue Fixation / Q000379:methods / Q000662:veterinary