Hyperoxia induces alkalinization and dome formation in MDCK epithelial cells.
We observed that confluent Madin-Darby canine kidney (MDCK) epithelial cells exposed to 95% O2 showed intensive dome formation, a manifestation of cell differentiation and transepithelial fluid transport, whereas cells exposed to 40% O2 or to normoxia did not. Hyperoxia-induced dome formation (HIDF) was preceded and accompanied by a significant rise in intracellular pH (pHi) on days 2 (7.53 vs. 7.42) and 3 (7.62 vs. 7.45), as compared with controls. Inhibition of the Na(+)-H+ exchanger by 0.1 or 1.0 mM amiloride caused 29 or 69% reduction of HIDF and completely abolished hyperoxia-induced alkalinization of the cells. HIDF was altered by modification of extracellular pH (pHo); there was a decrease by 84% with pHo 6.8, while pHo 7.8 led to earlier and more intensive dome formation (day 2, +472%; day 3, +27%). We also found that adenosine 3',5'-cyclic monophosphate (cAMP) was increased in hyperoxic cells, a change that was independent from the rise of pHi. We conclude that high-level hyperoxia induces dome formation in MDCK epithelial monolayers by a process involving activation of the Na(+)-H+ exchanger, together with increased intracellular cAMP.
Dreher
D
D
Respiratory Division, University Hospital, Geneva, Switzerland.
Rochat
T
T
D000468:Alkalies / Q000378:metabolism*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002460:Cell Line; D003470:Culture Media; D000242:Cyclic AMP / Q000378:metabolism; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism / Q000648:ultrastructure; D005452:Fluoresceins; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D007668:Kidney / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D010100:Oxygen / Q000378:metabolism*; D010539:Permeability; D011506:Proteins / Q000378:metabolism; D013997:Time Factors
D000468:Alkalies; D001639:Bicarbonates; D003470:Culture Media; D005452:Fluoresceins; D011506:Proteins; D000584:Amiloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D000242:Cyclic AMP; D010100:Oxygen