Increased nasal potential difference and amiloride sensitivity in neonates with cystic fibrosis Patients with cystic fibrosis (CF) have an increased nasal transepithelial potential difference (PD) which reflects increased sodium absorption across epithelium relatively impermeable to chloride. To evaluate nasal epithelial function in neonates with CF, the PD was recorded and the voltage response to superfusion of 10-SM amiloride, an inhibitor of sodium transport, measured between a Ringer perfused bridge on the nasal mucosa and a reference electrode in the subcutaneous space. We studied three neonates with CF with meconium ileus and compared the results with those in 24 term healthy neonates, including one obligate heterozygote for CF, and 27 control neonates with disease. All three CF neonates had raised sweat chloride values (mean 100 mEq/L) at 2 months. The CF neonates had higher PDs (-64.0 _+ 8.4 mV) than those in normal (-24.4 _+ 2.0 mY) or control (-25.8 _+ 2.0 mY) neonates. Superfusion with amiloride induced a 72% reduction in PDin the CF neonates as compared with healthy (37.5 _ 1.0%) and diseased (36.0 _+ 1.3%) neonates. The PD and amiloride response in CF neonates are similar to those in CF infants (2-24 months), older CF children (>6 years), and CF adults (-64.9 ___ 9.3 mV; 77.7 _+ 1.8%, n = 51). These results suggest that (I) nasal epithelial dysfunction is present in patients with CF shortly after birth, and (2) the nasal PD may be a diagnostic adjunct to the sweat test in the early diagnosis of CF. (J PEDIATR 1986;108:517-521) C. W. Gowen, M.D., E. E. Lawson, M.D., J. Gingras-Leatherman, M.D., J. T. Gatzy, Ph.D., R. C. Boucher, M.D., and M. R. Knowles, M.D. From the Departments of Medicine, Pharmacology, and Pediatrics, University of North Carolina School of Medicine, Chapel Hill Cystic fibrosis is an inherited disease that is manifest in many organ systems. The respiratory tract dysfunction appears to reflect abnormal airway secretions, which Supported by Grants HL00787, HL22924, and HDI9117, and Research Career Development Award 5-K04-HD00475-03 from the National Institutes of Health, and by RRDP Grant R003 6-03 from the Cystic Fibrosis Foundation. Presented in part at the Annual Meeting of the Society for Pediatric Research, May 1985. Submitted for publication Aug. 27, 1985; accepted Oct. 29, 1985. Reprint requests: Michael R. Knowles,M.D., Division of Pulmo- nary Diseases, 724 Burnett-Womack BuildingS' 229H, University of North Carolina, Chapel Hill, NC 27514. predispose to obstruction and chronic infection of the airways, j To date there has been no satisfactory explana- tion for the abnormal characteristics of airway secretions. A search for abnormal constituents of airway surface liquid has failed to identify unique mucus glycoproteins.2 However, because the epithelium of the sweat duct and CF Cystic Fibrosis PD Potential difference respiratory tract in patients with CF does not transport ions normally, it has been suggested that dysfunction in the regulation of the water and ionic content of secretions may play an important role in the pathophysiology of CF. a The net flux of ions across the respiratory epithelium 517