Immunofluorescent localization of cystic fibrosis transmembrane conductance regulator (CFTR) and epithelial sodium channel (ENaC) in human sweat ducts

Abstract

A functional link between the chloride channel cystic fibrosis transmembrane conductance regulator (CFTR) and the epithelial Na+ channel (ENaC), has been suggested based on evidence from electrophysiological and biochemical methods in heterologous expression systems. Their interaction in native tissue is not clearly defined but is implicated in the pathophysiology of cystic fibrosis. The present study utilized immunofluorescence and laser confocal microscopy on cryosections of healthy human skin specimens to characterize CFTR and ENaC localization in sweat ducts. Ductal segment morphology was identified with 4',6‐diamidino‐2‐phenylindole nuclear staining. Throughout the duct there was one to two fold less staining of CFTR compared to ENaC. The proportion of lumen‐specific staining was significantly (one to ten fold) greater for CFTR than for the more ubiquitous ENaC, but varied widely between tissue samples. There is additional corroborating evidence of some co‐localization of CFTR and ENaC confined primarily to the ductal lumen, a principal site of transepithelial NaCl reabsorption. This study is the first example of immunofluorescent staining for CFTR and ENaC localization in native human tissue. Future studies will help identify the spatial relationship between these two channel proteins, and how their potential interaction correlates to fluid and electrolyte transport in health and disease.

Harvesting and manipulating sweat and interstitial fluid in microfluidic devices

“…117 Cystic fibrosis (CF) leads to elevated levels of Na + and Cl − in sweat. 118 Usually, the rate of generation of Na + and Cl − is greater than the reabsorption rate during active perspiration. Hence, the concentration of Na + and Cl − increases with exercise.…”