Cytosolic Ca2+ and adenylyl cyclase responses in phenotypically distinct pulmonary endothelial cells.
Pulmonary microvascular endothelium forms a tighter barrier than does pulmonary artery endothelium; the mechanism of this important phenotypic difference is uncertain. We examined two regulators of endothelial permeability, cytosolic Ca2+ concentration ([Ca2+]i) and adenosine 3',5'-cyclic monophosphate (cAMP), in microvascular (PMVEC) and pulmonary conduit artery (PAEC) endothelium. Both resting and stimulated [Ca2+]i were lower in PMVEC compared with PAEC (resting [Ca2+]i, 94 +/- 7 vs. 123 +/- 8 nM; ATP-stimulated peak, 1.04 +/- 0.14 vs. 1.98 +/- 0.13 microM). Sustained Ca2+ transients in response to either ATP or thapsigargin were reduced in PMVEC compared with PAEC (ATP, 199 +/- 22 vs. 411 +/- 43 nM; thapsigargin, 195 +/- 13 vs. 527 +/- 65 nM), suggesting reduced Ca2+ influx in PMVEC. Reduced Ca2+ influx in PMVEC was confirmed by Mn2+ quenching and patch-clamp experiments. mRNA for Ca(2+)-inhibitable and protein kinase C-stimulated adenylyl cyclases was detected in both cell types. Whereas ATP caused a [Ca2+]i-mediated decrease in cAMP in PAEC, ATP caused a protein kinase C-mediated increase in cAMP in PMVEC. We conclude that PMVEC express a unique phenotype that favors enhanced barrier function through attenuated Ca2+ influx and preservation of cAMP content.
Stevens
T
T
Department of Anesthesiology, University of Colorado Health Sciences Center, Denver 80262, USA.
Fouty
B
B
Hepler
L
L
Richardson
D
D
Brough
G
G
McMurtry
I F
IF
Rodman
D M
DM
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005260:Female; D008345:Manganese / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010641:Phenotype; D011493:Protein Kinase C / Q000502:physiology; D011652:Pulmonary Circulation; D012333:RNA, Messenger / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology
D012333:RNA, Messenger; D008345:Manganese; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011493:Protein Kinase C; D000262:Adenylyl Cyclases; D002118:Calcium