It has been recently demonstrated that human esophageal submucosal mucous glands exhibit the ability to secrete copious amounts of mucin, well known within the gastrointestinal tract for its protective quality against hydrogen ion and pepsin. Since mucin may also play a protective role within the esophageal compartment, we have studied the rate of secretion of esophageal mucin in patients with RE. Mucin was assessed by periodic acid-Schiff methodology in esophageal secretion collected during continuous perfusion with saline (period I) followed by HCl (period II), HCl/pepsin (period III), and final saline (period IV), mimicking the natural gastroesophageal scenario. The basal rate of the luminal release of mucin in patients with grade II RE was 18% lower as compared with controls. During exposure of the esophageal mucosa to an HCl/pepsin solution, esophageal mucin output in the RE group was 52% lower than in the control group (0.154 +/- 0.027 vs 0.320 +/- 0.049 mg/cm2/min; P = 0.025). Furthermore, the rates of esophageal mucin output in patients with grade III RE during esophageal perfusion with saline and HCl/pepsin were 62% (0.090 +/- 0.021 vs 0.239 +/- 0.036 mg/cm2/min; P = 0.016) and 86% (0.048 +/- 0.010 vs 0.320 +/- 0.049 mg/cm2/min; P = 0.001) lower when compared with corresponding values in controls. After endoscopic healing of RE, the overall impairment in the rate of esophageal mucin secretion in patients with grade II improved from 31% to 17% at the end of therapy, whereas in patients with grade III the impairment in mucin secretion improved only marginally from 71% to 69%.(ABSTRACT TRUNCATED AT 250 WORDS)