O2 can raise fetal pneumocyte Na+ conductance without affecting ENaC mRNA abundance.
In fetal pneumocytes, increasing P(O(2)) can raise apical Na(+) conductance (G(Na(+))) and increase the abundance of epithelial Na(+) channel subunit (alpha-, beta-, and gamma-ENaC) mRNA, suggesting that the rise in G(Na(+)), which may be important to the perinatal maturation of the lung, reflects O(2)-evoked ENaC gene expression. However, we now show that physiologically relevant increases in P(O(2)) do not affect alpha-, beta-, and gamma-ENaC mRNA abundance in pneumocytes maintained (approximately 48 h) in hormone-free medium or in medium supplemented with dexamethasone and tri-iodothyronine, although the response does persist in cells maintained in medium containing a complex mixture of hormones/growth factors. However, parallel electrometric studies revealed clear increases in G(Na(+)) under all tested conditions and so it is now clear that O(2)-evoked increases in G(Na(+)) can occur without corresponding increases in ENaC mRNA abundance. It is therefore unlikely that this rise in G(Na(+)) is secondary to O(2)-evoked ENaC gene expression.
Richard
Kerry
K
Lung Membrane Transport Group, Tayside Institute of Child Health, Department of Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK.
Ramminger
Sarah J
SJ
Inglis
Sarah K
SK
Olver
Richard E
RE
Land
Stephen C
SC
Wilson
Stuart M
SM
D000818:Animals; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D003907:Dexamethasone / Q000494:pharmacology; D004553:Electric Conductivity; D053503:Epithelial Sodium Channels; D005333:Fetus / Q000166:cytology; D005786:Gene Expression Regulation; D010100:Oxygen / Q000494:pharmacology*; D010313:Partial Pressure; D011650:Pulmonary Alveoli / Q000166:cytology / Q000196:embryology* / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D015222:Sodium Channels / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology*; D014284:Triiodothyronine / Q000494:pharmacology
D016895:Culture Media, Serum-Free; D053503:Epithelial Sodium Channels; D012333:RNA, Messenger; D015222:Sodium Channels; D014284:Triiodothyronine; D003907:Dexamethasone; D010100:Oxygen