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Role of Nitric Oxide Pathway in Placental Dysfunction Following Fetal Bypass
Christopher Lam, BS, R. Scott Baker, BS, Jerri McNamara, CCP, Robert Ferguson, CCP, John Lombardi, CCP, Kenneth Clark, PhD, Pirooz Eghtesady, MD, PhD The Annals of Thoracic Surgery Volume 84, Issue 3, Pages (September 2007) DOI: /j.athoracsur Copyright © 2007 The Society of Thoracic Surgeons Terms and Conditions
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Fig 1 Schematic representation of the nitric oxide–cyclic guanosine monophosphate (cGMP) signal transduction pathway leading to vasodilation. Nitric oxide (NO) synthesis from L-arginine is catalyzed by nitric oxide synthase (NOS). Rapid degradation of released NO produces citrulline and nitrates. Stimulation of guanylate cyclase activity by NO increases the production of cGMP. Degradation of cGMP is regulated by cGMP-specific phosphodiesterase-5 (PDE-5). Vasodilation is induced by increases in cGMP levels. (GTP = guanosine triphosphate.) The Annals of Thoracic Surgery , DOI: ( /j.athoracsur ) Copyright © 2007 The Society of Thoracic Surgeons Terms and Conditions
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Fig 2 Fetal arterial blood gases with cardiopulmonary bypass. Plasma concentrations of (A) lactate, (B) pCO2, (C) pH, and (D) pO2 and oxygen saturation (SO2) are shown for control animals (dashed lines) and experimental animals (solid lines). These variables were measured before bypass (pre Bypass), at 15 and 30 minutes of bypass, and at 30, 90, and 120 minutes after (Post) bypass. *p ≤ 0.05 comparing in-group versus prebypass (baseline). (In [D], solid lines with diamonds = bypass PO2; solid lines with triangles = bypass SO2; dashed lines with squares = control PO2; dashed lines with circles = control SO2.) The Annals of Thoracic Surgery , DOI: ( /j.athoracsur ) Copyright © 2007 The Society of Thoracic Surgeons Terms and Conditions
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Fig 3 Placental in-vivo concentrations of nitric oxide (NO) with cardiopulmonary bypass. The data are presented as percent changes in mean NO concentrations in experimental and control animals compared with values before bypass. In the bypass group (open bars [n = 7]), NO levels rose during the bypass period but gradually decreased after the bypass period, whereas the control group (solid bars [n = 6]) did not diverge from baseline. The Annals of Thoracic Surgery , DOI: ( /j.athoracsur ) Copyright © 2007 The Society of Thoracic Surgeons Terms and Conditions
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Fig 4 Representative changes in-vivo nitric oxide (NO) concentrations (solid line) compared with umbilical blood flow (broken line) in an experimental fetus. Changes in umbilical blood flow (scale on left axis) paralleled changes in NO concentrations (scale on right axis), increasing during the 30-minute bypass procedure. Changes with cannulation before bypass (pre Bypass), and 30 and 60 minutes after bypass (post) until fetal demise are shown. The Annals of Thoracic Surgery , DOI: ( /j.athoracsur ) Copyright © 2007 The Society of Thoracic Surgeons Terms and Conditions
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Fig 5 Changes in fetal plasma concentrations of (A) nitric oxide (NO) metabolites and (B) cyclic guanosine monophosphate (cGMP) concentrations with bypass expressed as percentage change from baseline (pre Bypass). (A) There is a significant and marked decline in the bypass group (open bars [n = 14]) in plasma NO metabolites concentrations at the end of 30 minutes of bypass, and 30 minutes and 120 minutes after bypass (post) when compared with baseline. (B) Plasma cGMP concentrations increased significantly in experimental animals (open bars), at 30 minutes and 120 minutes after bypass (post) when compared with baseline. *p ≤ 0.05 compared in-group with baseline. (Control = solid bars [n = 6].) The Annals of Thoracic Surgery , DOI: ( /j.athoracsur ) Copyright © 2007 The Society of Thoracic Surgeons Terms and Conditions
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Fig 6 Representative pictures of phosphodiesterase-5 (PDE-5) expression in placental sections for (A, B, C) experimental animals and (D, E) control animals at ×100 magnification detected by immunofluorescence. Immunohistochemical localization of PDE-5 is markedly increased 30 minutes after bypass (B, arrow) in tissues of maternal origin, but returned to baseline 120 minutes after bypass (C), similar to controls (D, E, F). Results were consistent in all animals. The Annals of Thoracic Surgery , DOI: ( /j.athoracsur ) Copyright © 2007 The Society of Thoracic Surgeons Terms and Conditions
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