Thyroid hormone potentiates glucocorticoid-evoked airway Na+ transport without affecting alpha-ENaC transcription.
Glucocorticoid and thyroid hormones (T3) are important for the development of the lungs' Na+ absorbing phenotype, which is essential for the integrated functioning of the respiratory tract. Electrometric studies of H441 airway epithelial cells confirmed that dexamethasone increases apical Na+ conductance (GNa) and demonstrated that T3 facilitates this control over GNa. Assays of transcriptional activity showed that dexamethasone caused concentration-dependent activation of the human alpha-ENaC promoter (EC50 approximately 5 nM) but, despite its clear effect on GNa, T2 had no effect upon the transcriptional response to dexamethasone. The facilitation of Na+ transport may thus reflect control over events downstream to transcription.
Richard
K
K
Lung Membrane Transport Group, Division of Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, UK.
Ramminger
S J
SJ
Forsyth
L
L
Burchell
A
A
Wilson
S M
SM
D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D003907:Dexamethasone / Q000494:pharmacology*; D053503:Epithelial Sodium Channels; D006801:Humans; D016133:Polymerase Chain Reaction; D020545:Respiratory Mucosa / Q000187:drug effects / Q000502:physiology*; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects*; D014284:Triiodothyronine / Q000494:pharmacology*
D017931:DNA Primers; D053503:Epithelial Sodium Channels; D015222:Sodium Channels; D014284:Triiodothyronine; D003907:Dexamethasone