Relative expression of the human epithelial Na+ channel subunits in normal and cystic fibrosis airways.
The availability of the newly cloned subunits (alpha, beta, gamma) of the epithelial Na+ channel (ENaC) permits molecular studies of the pathogenesis of the abnormal Na+ transport rates of cystic fibrosis (CF) airway epithelia. Northern analyses of airway epithelia showed that both normal and CF airway epithelia express ENaC subunit mRNAs in a ratio of alpha > beta > gamma. In situ hybridization studies revealed expression of all three ENaC subunits in the superficial epithelium and the alpha- and beta-subunits in the gland ductular and acinar epithelium of both normal and CF airways. Ribonuclease protection assays revealed that the steady-state levels of alpha-, beta-, and gamma-ENaC mRNAs were similar in CF and normal airway superficial epithelia. These findings indicate that 1) Na+ transport defects in CF airways disease may be expressed in glandular acinar and ductal epithelium as well as superficial epithelium, and 2) the molecular pathogenesis of Na+ hyperabsorption in CF airways does not reflect increased levels of Na+ channel mRNAs, and probably number, but reflects an absence of the normal inhibitory regulation of Na+ channels by CF transmembrane conductance regulator proteins.
Burch
L H
LH
Department of Medicine, University of North Carolina at Chapel Hill 27599-7020, USA.
Talbot
C R
CR
Knowles
M R
MR
Canessa
C M
CM
Rossier
B C
BC
Boucher
R C
RC
D001483:Base Sequence; D015152:Blotting, Northern; D003550:Cystic Fibrosis / Q000378:metabolism*; D006801:Humans; D017403:In Situ Hybridization; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D009297:Nasal Mucosa / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D012016:Reference Values; D012260:Ribonucleases; D015222:Sodium Channels / Q000378:metabolism*
D015335:Molecular Probes; D015222:Sodium Channels; D012260:Ribonucleases