B A Hills1. 1. Department of Physiology, University of New England, Armidale, NSW.
Abstract
BACKGROUND: There is a growing body of evidence to indicate that the gastric mucosa is protected against the back-diffusion of acid by a physical barrier comprising surface-active phospholipid (SAPL) otherwise known as gastric surfactant on account of its similarity to pulmonary surfactant in composition and behaviour. AIMS: To determine whether this form of mucosal protection might extend into the oesophagus to offer some degree of protection against the reflux of gastric contents. METHODS: Oesophageal epithelium was tested for the same hydrophobicity which is characteristically imparted to gastric mucosa by SAPL. A morphological study was also performed to visualise any barrier, purposely avoiding conventional fixatives for electron microscopy which destroy hydrophobic surfaces. RESULTS: Oesophageal epithelium in the vicinity of the cardiac sphincter was found to be appreciably hydrophobic, although not as hydrophobic as gastric mucosa. This hydrophobicity was eliminated by bile salts selected as a known 'barrier breaker' and one which reacts with any lining of SAPL. The morphological study revealed much evidence of SAPL, especially that lining epithelial cells, while its source is probably the lamellar bodies also visualised. CONCLUSIONS: These findings indicate a physical barrier of oesophageal surfactant which could offer some degree of protection against gastro-oesophageal reflux but one which is particularly prone to attack by bile.
BACKGROUND: There is a growing body of evidence to indicate that the gastric mucosa is protected against the back-diffusion of acid by a physical barrier comprising surface-active phospholipid (SAPL) otherwise known as gastric surfactant on account of its similarity to pulmonary surfactant in composition and behaviour. AIMS: To determine whether this form of mucosal protection might extend into the oesophagus to offer some degree of protection against the reflux of gastric contents. METHODS: Oesophageal epithelium was tested for the same hydrophobicity which is characteristically imparted to gastric mucosa by SAPL. A morphological study was also performed to visualise any barrier, purposely avoiding conventional fixatives for electron microscopy which destroy hydrophobic surfaces. RESULTS: Oesophageal epithelium in the vicinity of the cardiac sphincter was found to be appreciably hydrophobic, although not as hydrophobic as gastric mucosa. This hydrophobicity was eliminated by bile salts selected as a known 'barrier breaker' and one which reacts with any lining of SAPL. The morphological study revealed much evidence of SAPL, especially that lining epithelial cells, while its source is probably the lamellar bodies also visualised. CONCLUSIONS: These findings indicate a physical barrier of oesophageal surfactant which could offer some degree of protection against gastro-oesophageal reflux but one which is particularly prone to attack by bile.