Role of calcium and calmodulin in flow-induced nitric oxide production in endothelial cells.
These experiments demonstrate that exposure of cultured endothelial cells (EC) to well-defined laminar fluid flow results in an elevated rate of NO production. NO production was monitored by release of NOx (NO2- + NO3(2-) and by cellular guanosine 3',5'-cyclic monophosphate (cGMP) concentration. NO synthase (NOS) inhibitor blocked the flow-mediated stimulation of both NOx and cGMP, indicating that both measurements reflect NO production. Exposure to laminar flow increased NO release in a biphasic manner, with an initial rapid production consequent to the onset of flow followed by a less rapid, sustained production. A similar rapid increase in NO production resulted from an increase in flow above a preexisting level. The rapid initial production of NO was not dependent on shear stress within a physiological range (6-25 dyn/cm2) but may be dependent on the rate of change in shear stress. The sustained release of NO was dependent on physiological levels of shear stress. The calcium (Ca2+) or calmodulin (CaM) dependence of the initial and sustained production of NO was compared with bradykinin (BK)-mediated NO production. Both BK and the initial production were inhibited by Ca2+ and CaM antagonists. In contrast, the sustained shear stress-mediated NO production was not affected, despite the continued functional presence of the antagonists. Dexamethasone had no effect on either the initial or the sustained shear stress-mediated NO production. An inducible NOS does not, therefore, explain the apparent Ca2+/CaM independence of the sustained shear stress-mediated NO production.(ABSTRACT TRUNCATED AT 250 WORDS)
Kuchan
M J
MJ
Department of Chemical Engineering, Pennsylvania State University, University Park 16802.
Frangos
J A
JA
D002118:Calcium / Q000502:physiology*; D002147:Calmodulin / Q000502:physiology*; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism* / Q000502:physiology*; D006801:Humans; D007477:Ions; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D009573:Nitrites / Q000378:metabolism; D013314:Stress, Mechanical
D002147:Calmodulin; D007477:Ions; D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide; D006152:Cyclic GMP; D002118:Calcium