Measurement of nasal potential difference in mild asthmatics.

STUDY OBJECTIVE To determine whether ion transport or barrier function across the nasal epithelium are altered in asthmatics. DESIGN In this pilot study, the nasal potential difference (PD) was measured using the technique established by Knowles and colleagues. A flowing agar bridge made electrical contact with the surface of the nasal epithelium along the floor of the nose. This bridge was referenced to a cutaneous electrode to determine the PD across the nasal epithelium. Changes in nasal PD in response to amiloride, chloride-free medium, and chloride-free medium containing isoproterenol were measured, and responses of asthmatics and healthy control subjects were compared. PARTICIPANTS Measurements were made in eight adult nonasthmatic subjects and 6 adult asthmatic subjects. All asthmatics had mild intermittent asthma. MEASUREMENTS AND RESULTS Continuous measurements of nasal PD were obtained while the nasal surface was perfused consecutively with saline solution (NaCl-containing solution), saline solution plus 100 micro mol/L amiloride, chloride-free solution plus amiloride, and chloride-free solution with amiloride plus 10 micro mol/L isoproterenol (a beta-adrenergic agonist). No significant differences in baseline PD or change in PD in response to changes in perfusate were found between the two groups. CONCLUSIONS Our results suggest that ion transport and barrier function of patients with mild asthma are normal. Therefore, by contrast to cystic fibrosis, changes in salt and water transport across airway epithelium may not contribute to accumulation of mucous secretions in asthma.