Tu1765 Regurgitation Can Indicate Either True Esophago-Pharyngeal Reflux (EPR) Event or Upper Esophageal Sphincter (UES) and Sub-Sphincter Proximal Esophageal Acid Exposure

Abstract

In prior studies we found that esophageal acid exposure caused a small decrease in airway diameter, an increase in tracheobronchial mucus secretion, and a decrease in mucociliary transport rate. However, the store of mucus is not large and can easily be depleted, therefore, we hypothesized that mucus production may be under physiological control. AIM: To determine whether a physiological stimulus can affect mucus production and to investigate the mechanism of this effect. METHODS: Sixteen cats were anesthetized using alphachloralose. The esophagus was ligated 3-4 cm from the UES and the esophagus proximal and distal to the ligation was cannulated. Either the proximal (N=8) or distal (N=8) esophagus was perfused using 0.1N HCl for 30 min followed by 30 min of PBS while the opposite esophageal segment was perfused with PBS for 60 min. The trachea was excised, fixed, sliced at 5μ, and stained with Periodic Acid Schiff (PAS)-Alcian Blue (AB) at pH 1.0. The areas of neutral (PAS-positive) and acidic (AB-positive) mucosubstances in the epithelial and submucosal mucous glands of the trachea adjacent to the proximal and distal cervical segments of esophagus perfused were quantified using Image J software. RESULTS: We found that the primary type of mucous of the epithelial and submucosal mucous cells was AB-positive and PAS-positive, respectively. Acid exposure of either esophageal segment caused a greater total and PAS-positive mucous content of the submucosal cells adjacent to the HCl-administered esophagus than adjacent to the PBS-administered esophagus (Table). CONCLUSIONS: The primary types of mucosubstances of the tracheal epithelial and submucosal cells are acidic and neutral respectively. Esophageal acid exposure increases mucus production of neutral mucosubstances of the tracheal submucosa probably through the previously identified local direct neural connection between the esophagus and trachea. We hypothesize that this pathway is part of the innate tracheal defense mechanism which prepares the trachea for acid exposure due to gastric reflux. Effects of HCl and PBS on Tracheal Mucous Content