Evidence for surfactant contributing to the gastric mucosal barrier of thehorse

This study was undertaken to determine the hydrophobicity of the luminal su rface of the equine stomach and to elucidate the ultrastructure of the lini ng imparting that property. Gastric and duodenal mucosal samples from 5 hor ses were collected immediately after euthanasia and subjected to surface co ntact angle measurement using a goniometer. Gastric mucosal samples from 4 horses and a foal were examined by electron microscopy following a fixation procedure known to preserve phospholipids and oligolamellar structures. Co ntact angles for the equine gastric glandular mucosal surface (mean +/- s.e . 78.0 +/- 11.0 degrees) were greater than for the duodenum (33.4 +/- 8.7 d egrees), (P = 0.003). The contact angles for gastric squamous tissue (50.4 +/- 4.5 degrees) tended to be greater than for duodenum (P = 0.15). Electro n microscopy revealed the existence of surfactant as abundant osmiophilic p hospholipid material within both squamous and glandular gastric mucosae. Th ese results indicate the hydrophobic nature of the equine gastric mucosae. We propose that the water-repellent nature of the stomach contributes to th e 'gastric mucosal barrier' and is imparted by surface-active phospholipid adsorbed to the surface. Phospholipids may also be utilised as a physical b arrier to back-diffusion of acid by Lining intracellular canaliculi and oxy ntic ducts where other defence mechanisms are absent.