Gastric mucosal barrier: hydrophobic lining to the lumen of the stomach.

The contact angle subtended between a droplet of aqueous fluid and nonwettable surfaces provides a direct estimation of their degree of hydrophobicity. The mean contact angle recorded in dogs at the oxyntic mucosal surface was 85.2 degrees, a value characteristic of acid-resistant substances such as polyethylene. This indicates that the mucosal surface of the stomach has a hydrophobic lining that may be attributed to the surface-active phospholipids known to be present in both the gastric mucosa and juice. Barrier breakers such as bile and aspirin were found virtually to eliminate the hydrophobicity. Hydrophobicity was found to be different in the esophagus, antrum, proximal and distal duodenum, and the colon but consistent with their resistance to acid attack. Endogenous surfactants are discussed for their capability to provide a cohesive and strongly adsorbed protective monolayer--a physical model for the gastric mucosal barrier compatible with the major properties of the gastric lining and many features of ulcerogenesis, including the protection afforded by prostaglandins.