Ultrastructure of the hydrophobic gastric surfactant barrier in the dog

Objectives To confirm the hydrophobicity of the luminal surface of the cani ne stomach and to elucidate the ultrastructure of the lining imparting that property. Design and procedures 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 mic roscopy 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 o smiophilic phospholipid material within the gastric and duodenal mucosae. Conclusion We have confirmed the hydrophobic nature of the canine gastric m ucosa whereas the luminal surface of the duodenum is hydrophilic. We propos e 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 surfa ce. Both gastric and duodenal mucosae may also utilise phospholipids as an intercellular defense mechanism in the event that tight junctions are breac hed by acid. It is tempting to speculate that a deficiency of gastric phosp holipids may predispose dogs to ulcers. Further, exogenous administration o f phospholipids may be useful in preventing gastric ulceration.