nitroarginine and Lung-Diseases

We designed the present experiments to investigate the involvement of endogenous nitric oxide synthase (NOS) inhibitors, dimethylarginine dimethylaminohydrolase (DDAH) as a hydrolyzing enzyme of the NOS inhibitors, NOS, arginase which shares l-arginine as a common substrate with NOS, and endothelin-1 (ET-1) in the pulmonary dysfunction after induction of experimental subarachnoid hemorrhage (SAH) in the rabbit. SAH was induced by injecting autologous blood into the cisterna magna, and controls were injected with saline. On day 2, pulmonary arteries were isolated for determinations. A significant impairment of the endothelium-dependent relaxation (EDR) caused by acetylcholine was found in 20 cases (43.5%) out of 46 SAH animals, and the same animals exhibited accompanying the significantly impaired cyclic GMP production, accumulated endogenous NOS inhibitors, attenuated DDAH activity, enhanced arginase activity and accumulated ET-1 within the vessel wall. Meanwhile, there were no differences in endothelial NOS activity per se and sodium nitroprusside-induced relaxation between the animals with an impaired EDR and those without such a change. ET-1 content within aortic wall was increased with concomitant decrease in cyclic GMP production after the intraperitoneal application of authentic monomethylarginine as a NOS inhibitor in the rat. The current results suggest that accumulated endogenous NOS inhibitors and enhanced arginase activity possibly bring about the impaired NO production, thereby attenuating the EDR and contributing to the accumulation of ET-1 within the vessel wall. The accumulated endogenous NOS inhibitors at least partly result from the decreased DDAH activity. These alterations may be relevant to the pulmonary dysfunction after induction of SAH.

Topics: Acetylcholine; Amidohydrolases; Animals; Arginase; Cyclic GMP; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Endothelin-1; Indomethacin; Lung Diseases; Male; Models, Biological; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; omega-N-Methylarginine; Oxadiazoles; Pulmonary Artery; Quinoxalines; Rabbits; Rats; Rats, Sprague-Dawley; Subarachnoid Hemorrhage; Vasoconstriction

Cyclooxygenase (COX) products and nitric oxide (NO) inhibit hypoxic pulmonary vasoconstriction (HPV), and their release could contribute to alterations in gas exchange in lung injury. We tested the hypothesis that combined blockade of COX and NO synthase (NOS) could further increase HPV and better protect gas exchange in lung injury than could blockade of either COX or NOS alone. We determined pulmonary vascular pressure-flow relationships in pentobarbital-anesthetized and ventilated dogs submitted to hypoxic challenges before and after administration of solvent (n = 4), indomethacin alone (2 mg/kg intravenously, n = 8), Nomega-nitro-L-arginine (L-NA) alone (10 mg/kg intravenoulsy, n = 8), indomethacin followed by L-NA (n = 8), and L-NA followed by indomethacin (n = 8). All of the dogs so treated then received oleic acid (0.06 ml/kg intravenously) to induce lung injury. Blood flow was manipulated by establishing a femoral arteriovenous bypass or by inflating an inferior vena caval balloon. Gas exchange was evaluated by measuring arterial PO2 and intrapulmonary shunt (using the inert gas sulfur hexafluoride) at identical cardiac outputs. The magnitude of HPV was not affected by solvent. Indomethacin and L-NA given separately enhanced HPV. L-NA added to indomethacin further enhanced HPV, as did indomethacin added to L-NA. After oleic acid-induced lung injury, gas exchange deteriorated less in dogs pretreated with indomethacin than in dogs pretreated with solvent or with L-NA alone. These results suggest that in pentobarbital-anesthetized dogs: (1) the magnitude of HPV is limited by the corelease of COX metabolites and of NO; and (2) inhibition of COX, but not of NOS, attenuates the deterioration of gas exchange in oleic acid-induced lung injury.

Topics: Animals; Blood Pressure; Cyclooxygenase Inhibitors; Dogs; Enzyme Inhibitors; Hypoxia; Indomethacin; Lung Diseases; Nitric Oxide Synthase; Nitroarginine; Oleic Acid; Pulmonary Circulation; Vasoconstriction

Both nitric oxide and arachidonic acid metabolites have been implicated in pathogenesis of septic shock. We have recently described a model of endotoxin-induced acute lung injury in rats in which nitric oxide synthase is inhibited. The possible interplay between nitric oxide and eicosanoids (thromboxane A2, prostacyclin) in this model have been presently studied. Animals were randomly assigned to four experimental groups which received the following treatment. 1. Lipopolysaccharide (LPS) infusion only, 2 mg.kg-1min-1 during 10 min (LPS group). 2. N omega-Nitro-L-Arginine 10 mg.kg-1 (L-NNA, nitric oxide synthase inhibitor) pretreatment followed by LPS infusion (L-NNA + LPS group). 3. L-NNA and camonagrel 25 mg.kg-1 (CAM, thromboxane synthase inhibitor) pretreatment followed by LPS infusion (L-NNA + CAM + LPS group). 4. L-NNA and iloprost 0.3 microgram.kg-1.min-1(ILO, stable analog of prostacyclin) pretreatment followed by LPS infusion (L-NNA + ILO + LPS group). LPS infusion resulted in a biphasic response in mean arterial blood pressure. A transient but deep fall in arterial blood pressure was followed by a long-lasting hypotension that led to death after 278 +/- 49 min. L-NNA + LPS rats died within 22 +/- 5 min among the symptoms of systemic hypotension and acute lung injury. In L-NNA + CAM + LPS group a significant attenuation of early phase of hypotension occurred and survival time was comparable with that of the LPS group (298 +/- 68 min). In rats of the L-NNA + ILO + LPS group survival time increased insignificantly to 48 +/- 41 min. It is concluded that immediate deleterious effects of lipopolysaccharide in NO-deficient rats are at least partially mediated by thromboxane A2 while prostacyclin cannot replace NO in its pneumoprotective action.

Topics: Animals; Blood Pressure; Epoprostenol; Escherichia coli; Indans; Lipopolysaccharides; Lung Diseases; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley; Thromboxane A2; Thromboxane-A Synthase

Inhibitors of endothelium-derived nitric oxide synthesis or activity have been reported to enhance hypoxic vasoconstriction in isolated lung preparations. We hypothesized that methylene blue, a guanylate cyclase inhibitor, and N omega-nitro-L-arginine, a nitric oxide synthase inhibitor, would increase pulmonary vascular tone and improve gas exchange in anesthetized and ventilated (inspired O2 fraction 0.4) dogs with oleic acid (OA) lung injury. Mean pulmonary arterial pressure-(Ppa) flow (Q) relationships (generated by a manipulation of venous return, which was increased by opening a femoral arteriovenous bypass or decreased by inflating an inferior vena cava balloon) and gas exchange (evaluated by arterial blood gases and SF6 intrapulmonary shunt determinations) were investigated before and after OA (0.06 ml/kg i.v.) and again after solvent (n = 8), methylene blue (8 mg/kg i.v., n = 10), or N omega-nitro-L-arginine (40 mg/kg i.v., n = 8) in a randomized order. OA administration induced pulmonary hypertension, decreased arterial PO2, and increased intrapulmonary shunt. After OA, solvent had no effect on pulmonary hemodynamics and gas exchange. Both methylene blue and N omega-nitro-L-arginine further increased Ppa at all levels of Q. Only methylene blue, however, improved gas exchange after OA (arterial PO2 from 71 +/- 6 to 89 +/- 12 Torr and intrapulmonary shunt from 44 +/- 6 to 34 +/- 6%, both P < 0.02). These results suggest that nitric oxide is released during OA lung injury and modulates pulmonary hypertension. Whether nitric oxide impairs the regulation of gas exchange in OA lung injury remains uncertain, however.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Blood Gas Analysis; Blood Pressure; Cardiac Output; Dogs; Guanylate Cyclase; Lung Diseases; Methylene Blue; Muscle Tonus; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oleic Acids; Pulmonary Artery; Pulmonary Gas Exchange; Sulfur Hexafluoride