Large conductance Ca2+-activated K+ channels sense acute changes in oxygen tension in alveolar epithelial cells.
The rise in alveolar oxygen tension (PO(2)) that occurs as the newborn infant takes its first breaths induces removal of liquid from the lung lumen due to ion transport across the alveolar epithelium and the activity of alveolar Na(+) channel (ENaC). In the present study, we have aimed to identify an ion conductance in alveolar epithelial A549 cells that responds to acute changes in PO(2). Variation in PO(2) did not affect single-channel ENaC activity. However, in these cells we have detected single-channel conductance having properties similar to those of large conductance Ca(2+)-activated K(+) (BK(Ca)) channels. Reverse transcriptase-polymerase chain reaction and Western blotting demonstrated presence of alpha-BKCa channel subunit and iberiotoxin, a blocker of BK(Ca) channels, inhibited whole cell K(+) current. Chronic changes in PO(2) did not affect expression, recruitment, or function of BK(Ca) channels in A549 cells. In contrast, acute changes of PO(2) regulated the BK(Ca) channel activity by controlling the channel mean open time. This effect of PO(2) was insensitive to inhibitor of flavoproteins, diphenylene iodinium. In addition, decrease in PO(2) and iberiotoxin induced membrane depolarization and Ca(2+) oscillations in A549 cells. We conclude that BK(Ca) channels serve as oxygen sensors in human alveolar A549 epithelial cells.
Jovanović
Sofija
S
Tayside Institute of Child Health, Ninewells Hospital & Medical School, University of Dundee, Scotland, United Kingdom. a.javanovic@bundee.ac.uk
Crawford
Russell M
RM
Ranki
Harri J
HJ
Jovanović
Aleksandar
A
D002118:Calcium / Q000502:physiology*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D053503:Epithelial Sodium Channels; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009861:Onium Compounds / Q000494:pharmacology; D010100:Oxygen / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D015222:Sodium Channels / Q000378:metabolism
D004791:Enzyme Inhibitors; D053503:Epithelial Sodium Channels; D007473:Ion Channels; D009861:Onium Compounds; D010455:Peptides; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger; D015222:Sodium Channels; C007517:diphenyleneiodonium; C064719:iberiotoxin; D010100:Oxygen; D002118:Calcium