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Title

Effect of systemic nitric oxide synthase inhibition on optic disc oxygen partial pressure in normoxia and in hypercapnia
Authors
Petropoulos, Ioannis
Pournaras, Jean-Antoine C.
Stangos, Alexandros Athanasios
Pournaras, Constantin
Published in Investigative Ophthalmology & Visual Science. 2009, vol. 50, no. 1, p. 378-84
Abstract PURPOSE: To investigate the effect of systemic nitric oxide synthase (NOS) inhibition on optic disc oxygen partial pressure (PO(2)) in normoxia and hypercapnia. METHODS: Intervascular optic disc PO(2) was measured in 12 anesthetized minipigs by using oxygen-sensitive microelectrodes placed <50 microm from the optic disc. PO(2) was measured continuously during 10 minutes under normoxia, hyperoxia (100% O(2)), carbogen breathing (95% O(2), 5% CO(2)), and hypercapnia (increased inhaled CO(2)). Measurements were repeated after intravenous injection of N(omega)-nitro-L-arginine methyl ester (L-NAME) 100 mg/kg. Intravenous L-arginine 100 mg/kg was subsequently given to three animals. RESULTS: Before L-NAME injection, an increase was observed in optic disc PO(2) during hypercapnia (DeltaPO(2) = 3.2 +/- 1.7 mm Hg; 18%; P = 0.001) and carbogen breathing (DeltaPO(2) = 12.8 +/- 5.1 mm Hg; 69%; P < 0.001). Optic disc PO(2) in normoxia remained stable for 30 minutes after L-NAME injection (4% decrease from baseline; P > 0.1), despite a 21% increase of mean arterial pressure. Optic disc PO(2) increase under hypercapnia was blunted after L-NAME injection (DeltaPO(2) = 0.6 +/- 1.1 mm Hg; 3%; P > 0.1), and this effect was reversible by L-arginine. Moreover, L-NAME reduced the response to carbogen by 29% (DeltaPO(2) = 9.1 +/- 4.4 mm Hg; 49%; P = 0.01 versus before L-NAME). The response to hyperoxia was not affected. CONCLUSIONS: Whereas systemic NOS inhibition did not affect optic disc PO(2) in normoxia, a blunting effect was noted on the CO(2)-induced optic disc PO(2) increase. Nitric oxide appears to mediate the hypercapnic optic disc PO(2) increase.
Keywords Animals — Arginine/administration & dosage — Blood Pressure — Carbon Dioxide/administration & dosage — Enzyme Inhibitors/administration & dosage — Hypercapnia/blood — Hyperoxia/blood — Injections, Intravenous — Ion-Selective Electrodes — Microelectrodes — NG-Nitroarginine Methyl Ester/administration & dosage — Nitric Oxide Synthase Type II/antagonists & inhibitors — Optic Disk/blood supply — Oxygen/administration & dosage/blood — Oxygen Consumption/physiology — Partial Pressure — Swine — Swine, Miniature
Identifiers
PMID: 18676634
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Article (Author postprint) (262 Kb) - document accessible for UNIGE members only Limited access to UNIGE
Other version: http://www.iovs.org/cgi/content/full/50/1/378
Structures
Faculté de médecine / Section de médecine clinique / Département des neurosciences cliniques
Citation
(ISO format) 		PETROPOULOS, Ioannis et al. Effect of systemic nitric oxide synthase inhibition on optic disc oxygen partial pressure in normoxia and in hypercapnia. In: Investigative Ophthalmology & Visual Science, 2009, vol. 50, n° 1, p. 378-84. https://archive-ouverte.unige.ch/unige:1179

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Deposited on : 2009-03-19

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