Acute normoxia increases fetal pulmonary artery endothelial cell cytosolic Ca2+ via Ca2+-induced Ca2+ release.
To test the hypothesis that an acute increase in O(2) tension increases cytosolic calcium ([Ca(2+)](i)) in fetal pulmonary artery endothelial cells (PAECs) via entry of extracellular calcium and subsequent calcium-induced calcium release (CICR) and nitric oxide release, low-passage PAECs (<10 passages) were isolated from the intralobar pulmonary artery (PA) of fetal sheep and maintained under hypoxic conditions (Po(2), 25 Torr). Using the calcium-sensitive dye fura-2, we demonstrated that acute normoxia (Po(2) = 120 Torr) increased PAECs [Ca(2+)](i) by increasing the rate of entry of extracellular calcium. In the presence of either ryanodine or 2-aminoethoxy-diphenylborate (2APB), normoxia did not lead to a sustained increase in PAECs [Ca(2+)](i) Whole-cell patch clamp studies demonstrated that acute normoxia causes PAEC membrane depolarization. When loaded with the nitric oxide (NO)-sensitive dye, DAF - FM, acute normoxia increased PAEC fluorescence. In PAECs derived from fetal lambs with pulmonary hypertension, an acute increase in O(2) tension had no effect on either [Ca(2+)](i) or NO production. Hypoxia increases loading of acetylcholine-sensitive calcium stores, as hypoxia potentiated the response to acetylcholine We conclude that acute normoxia increases [Ca(2+)](i) and NO production in normotensive but not hypertensive fetal PAECs via extracellular calcium entry and calcium release from calcium-sensitive intracellular stores.
Tirosh
Raz
R
Department of Pediatrics, Division of Pediatric Pulmonary and Critical Care Medicine, University of Minnesota, Minneapolis, MN 55455, USA.
Resnik
Ernesto R
ER
Herron
Jean
J
Sukovich
David J
DJ
Hong
Zhigang
Z
Weir
E Kenneth
EK
Cornfield
David N
DN
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D005260:Female; D005333:Fetus / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D010100:Oxygen / Q000378:metabolism*; D011651:Pulmonary Artery / Q000378:metabolism*; D012756:Sheep
D009569:Nitric Oxide; D010100:Oxygen; D002118:Calcium