Am. J. Respir. Crit. Care Med., Volume 158, Number 4, October 1998, 1213-1220

Relation between , , and  Human Amiloride- Sensitive Epithelial Na⁺ Channel mRNA Levels and Nasal Epithelial Potential Difference in Healthy Men

GAIL OTULAKOWSKI, SUSANNE FLUECKIGER-STAUB, LYNDA ELLIS, KUMAR RAMLALL, OLIVIER STAUB, DAVID SMITH, PETER DURIE, and HUGH O'BRODOVICH

Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada

To analyze messenger RNA (mRNA) levels for the , , and  subunits of the human amiloride-sensitive epithelial Na⁺ channel (hENaC) in respiratory epithelia, we developed a competitive quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) assay specific for each subunit, using two human respiratory epithelial-cell lines. We next determined the relation between hENaC mRNA levels and the biologic activity of the hENaC in the respiratory epithelium of eight normal men. The electrical potential difference (PD) between the epithelium of the inferior nasal turbinate and the subcutaneous space was measured, using control and amiloride (100 µM) solutions. QRT-PCR measurement of hENaC-subunit mRNAs and epithelial-specific cytokeratin 18 mRNA allowed us to normalize hENaC expression to epithelial-cell RNA. Respective values for , , and  hENaC mRNA levels in epithelium obtained at the site of maximal PD were 39 ± 4.0, 7.5 ± 0.92, and 1.8 ± 0.25 attomol/fmol cytokeratin mRNA, respectively. Respiratory epithelial PD exhibited a significant negative correlation with  hENaC (r² = 0.72, p < 0.01), tended to increase with increasing  hENaC, and was unaffected by  hENaC mRNA levels. Our results suggest that hENaC activity in vivo is influenced by expression of the gene for  hENaC. The assay used in the study provides a useful tool for evaluating Na⁺-channel expression in clinically relevant patient populations.

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