Superoxide and endothelium-dependent constriction to flow in porcine small pulmonary arteries (original) (raw)
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American Journal of Physiology-Heart and Circulatory Physiology, 1999
The present study was aimed at examining the role of nitric oxide (NO) in the hypoxic contraction of isolated small pulmonary arteries (SPA) in the rat. Animals were treated with either saline (sham experiments) or Escherichia coli lipolysaccharide [LPS, to obtain expression of the inducible NO synthase (iNOS) in the lung] and killed 4 h later. SPA (300- to 600-μm outer diameter) were mounted as rings in organ chambers for the recording of isometric tension, precontracted with PGF2α, and exposed to either severe (bath [Formula: see text] 8 ± 3 mmHg) or milder (21 ± 3 mmHg) hypoxia. In SPA from sham-treated rats, contractions elicited by severe hypoxia were completely suppressed by either endothelium removal or preincubation with an NOS inhibitor [ N G-nitro-l-arginine methyl ester (l-NAME), 10−3 M]. In SPA from LPS-treated rats, contractions elicited by severe hypoxia occurred irrespective of the presence or absence of endothelium and were largely suppressed by l-NAME. The milder hy...
AJP: Heart and Circulatory Physiology, 2007
Congenital cardiac defects associated with increased pulmonary blood flow (Q p ) produce pulmonary hypertension. We have previously reported attenuated endothelium-dependent relaxations in pulmonary arteries (PA) isolated from lambs with increased Q p and pulmonary hypertension. To better characterize the vascular alterations in the nitric oxide-superoxide system, twelve fetal lambs underwent in-utero placement of an aorto-pulmonary vascular graft (shunt). Twin lambs served as controls. PA were isolated from these lambs at 4-6 weeks of age. Electron paramagnetic resonance spectroscopy on fourth generation PA showed significantly increased superoxide anion generation in shunt PA that were decreased to control levels following inhibition of nitric oxide synthase (NOS) with 2-Ethyl-2-thiopseudourea. Preconstricted fifth generation PA rings were relaxed with a NOS agonist (A23187), a NO donor (SNAP), polyethylene glycol conjugated superoxide dismutase (PEG-SOD), or H 2 O 2 . A23187, PEG-SOD and H 2 O 2 mediated relaxations were impaired in shunt PA compared to controls. Pretreatment with PEG-SOD significantly enhanced the relaxation response to A23187 and SNAP in shunt but not control PA. Inhibition of NOS with L-nitroarginine or scavenging superoxide anions with tiron enhanced relaxation to SNAP and inhibited relaxation to PEG-SOD in shunt PA. Pretreatment with catalase inhibited relaxation of shunt PA to A23187, SOD and H 2 O 2 . We conclude that NOS catalyzes the production of superoxide anions in shunt PA. PEG-SOD relaxes shunt PA by converting these anions to H 2 O 2 , a Page 3 of 39 Copyright Information 4 pulmonary vasodilator. The redox environment, influenced by the balance between production and scavenging of ROS, may have important consequences on pulmonary vascular reactivity in the setting of increased Q p .
British Journal of Pharmacology, 2001
1 Inhaled nitric oxide (iNO) is widely used in the treatment of pulmonary hypertension while inhaled NO donors have been suggested as an alternative therapy. The dierential susceptibility to inactivation by oxidative stress and oxyhaemoglobin of NO and two NO donors, sodium nitroprusside (SNP) and S-nitroso-N-acetyl-penicillamine (SNAP) were analysed in isolated endothelium-denuded pulmonary arteries from 2-week-old piglets stimulated with U46619. 2 NO, SNAP and SNP relaxed the arteries (pIC 30 =7.73+0.12, 7.26+0.17 and 6.43+0.13, respectively) but NO was not detected electrochemically in the bath after the addition of SNP and only at concentrations at which SNAP produced more than 50% relaxation. 3 The sGC inhibitor ODQ (10 76 M) or the sarcoplasmic Ca 2+ -ATPase thapsigargin (2610 76 M) markedly inhibited the relaxation induced by NO, SNAP and SNP. 4 Addition of oxyhaemoglobin (3610 77 M) or diethyldithiocarbamate (1 mM) markedly inhibited NO-(pIC 30 =6.88+0.07 and 6.92+0.18, respectively), weakly inhibited SNAP-and had no eect on SNP-induced relaxation. Xanthine oxidase (5 mu ml 71 ) plus hypoxanthine (10 74 M) markedly inhibited NO-(pIC 30 =6.96+0.12) but not SNAP-or SNP-induced relaxation. 5 Superoxide dismutase (SOD), MnCl 2 , diphenileneiodonium and exposing the luminal surface of the rings outwards (inversion) potentiated the relaxant responses of NO (pIC 30 =8.52+0. 16, 8.23+0.11, 8.01+0.11 and 8.20+0.10, respectively). However, SOD did not modify the NO detected by the electrode and had no eect on SNAP-or SNP-induced relaxation. 6 Therefore, the kinetics and local distribution of NO release of NO donors in¯uence the susceptibility to the scavenging eects of oxyhaemoglobin and superoxide.
British Journal of Pharmacology, 2003
1 Chronic hypoxia (CH) increases lung tissue expression of all types of nitric oxide synthase (NOS) in the rat. However, it remains unknown whether CH-induced changes in functional and histological NOS distributions are correlated in rat small pulmonary arteries. 2 We measured the effects of NOS inhibitors on the internal diameters (ID) of muscular (MPA) and elastic (EPA) pulmonary arteries (100 -700 mm ID) using an X-ray television system on anaesthetized rats. We also conducted NOS immunohistochemical localization on the same vessels. 3 Nonselective NOS inhibitors induced ID reductions in almost all MPA of CH rats (mean reduction, 3673%), as compared to B60% of control rat MPA (mean, 1072%). The inhibitors reduced the ID of almost all EPA with similar mean values (B26%) in both CH and control rats. On the other hand, inducible NOS (iNOS)-selective inhibitors caused ID reductions in B60% of CH rat MPA (mean, 1573%), but did so in only B20% of control rat MPA (mean, 272%). This inhibition caused only a small reduction (mean, B4%) in both CH and control rat EPA. A neuronal NOSselective inhibitor had no effect. 4 The percentage of endothelial NOS (eNOS)-positive vessels was B96% in both MPA and EPA from CH rats, whereas it was 51 and 91% in control MPA and EPA, respectively. The percentage for iNOS was B60% in both MPA and EPA from CH rats, but was only B8% in both arteries from control rats. 5 The data indicate that in CH rats, both functional and histological upregulation of eNOS extensively occurs within MPA. iNOS protein increases sporadically among parallel-arranged branches in both MPA and EPA, but its vasodilatory effect is predominantly observed in MPA. Such NOS upregulation may serve to attenuate hypoxic vasoconstriction, which occurs primarily in MPA and inhibit the progress of pulmonary hypertension.
Involvement of endothelial NO in the dilator effect of VIP on rat isolated pulmonary artery
Regulatory Peptides, 2007
The endothelium and its interaction with smooth muscle play a central role in the local control of the pulmonary vasculature, and endothelial dysfunction is thought to contribute to pulmonary hypertension and chronic obstructive pulmonary disease. Vasoactive intestinal peptide (VIP), a 28-amino acid neuropeptide, relaxes the rat pulmonary artery, but there is controversy as to whether or not this action of VIP depends on the endothelium. The aim of this study, therefore, was to investigate the role of the endothelium and nitric oxide (NO), the major endothelium-derived relaxing factor, in the dilator action of VIP on the rat isolated pulmonary artery. Pulmonary artery preparations pre-contracted by the α 1adrenoceptor agonist L-phenylephrine were relaxed by VIP (0.003-1 μM) and acetylcholine (0.003-10 μM) in a concentration-dependent manner. Mechanical removal of the endothelium reduced the maximal response to VIP by about 50% and practically abolished the response to acetylcholine. Inhibition of NO synthesis by N ω -nitro-L-arginine methyl ester (0.5 mM) had a similar effect, abolishing the vasorelaxation caused by acetylcholine and attenuating the vasorelaxation caused by VIP by about 50%. From these data it is concluded that the relaxant action of VIP on the rat isolated pulmonary artery depends in part on the presence of the endothelium and that this part is mediated by endothelial NO.
Pediatric Research, 2003
The superoxide anion (O 2 ⅐Ϫ) appears to be an important modulator of nitric oxide bioavailability. Enzymatic scavenging of O 2 ⅐Ϫ is carried out by superoxide dismutase (SOD). The present study was designed to characterize the developmental changes on pulmonary vascular reactivity induced by 1) exogenous Cu/Zn SOD, 2) several putative SOD mimetics, and 3) endogenous SOD inhibition. We also analyzed age-related changes on pulmonary SOD activity and vascular O 2 ⅐Ϫ levels. SOD (1-300 U/mL) produced endotheliumdependent relaxation of U46619-contracted intrapulmonary arteries (fourth branch) and veins from 12-to 24-hold and 2-wk-old piglets. SOD-induced relaxation was greater in pulmonary arteries and was abolished by the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester. SOD induced a greater pulmonary artery relaxation in the 2-wk-old than in the 12-to 24-hold piglet. SOD (100 U/mL) did not modify acetylcholine-induced relaxation in pulmonary arteries. In contrast, endogenous SOD inhibition by diethyldithiocarbamate (3 mM) impaired acetylcholine-induced relaxation in pulmonary arteries from newborn but not from 2-wk-old piglets. Total SOD activity in lung tissue did not change with postnatal age. With the use of dihydroethidium, an oxidant-sensitive fluorescent probe, we did not find significant age-or vessel-related differences in O 2 ⅐Ϫ presence. From the putative SOD mimetics tested, only the metal salts MnCl 2 and CuSO 4 reproduced the vascular effects of SOD. In summary, SOD produces endothelium-dependent pulmonary vascular relaxation by protecting nitric oxide from destruction by O 2 ⅐Ϫ. This effect was less marked in newborns than in 2-wk-old piglets. In contrast, pulmonary arteries from newborn piglets are more sensitive to the inhibition of endogenous SOD. (Pediatr Res 54: 372-381, 2003) Abbreviations ACh, acetylcholine DETCA, diethyldithiocarbamate DHE, dihydroethidium L-NAME, N-nitro-L-arginine methyl ester MnTMPyP, Mn [III] tetrakis [1-methyl-4-pyridyl] porphyrin NBT, nitro blue tetrazolium NO ⅐ , nitric oxide ONOO ؊ , peroxynitrite PEG-SOD, polyethylene glycosylated SOD PPHN, persistent pulmonary hypertension of the newborn PTIYO, 4-phenyl-2,2,5,5-tetramethyl imidazolin-1-yloxy-5oxide SOD, superoxide dismutase U46619, 9,11-dideoxy-11␣,9␣-epoxymethano-prostaglandin F 2␣
The Journal of physiology, 1994
1. The actions of inhibitors of the release or action of nitric oxide (NO) on pulmonary vascular resistance (PVR) were investigated in lungs isolated from pig, sheep, dog and man. 2. In pig, sheep and human lungs perfused with Krebs-dextran solution, both N omega-nitro-L-arginine methyl ester (L-NAME; 10(-5) M) and Methylene Blue (10(-4) M) increased basal PVR. This increase was reversed by sodium nitroprusside (10(-5) M). In pig lungs N omega-monomethyl-L-arginine (10(-4) M) increased PVR by 154%. This increase was partially reversed by L-arginine (10(-3) M). L-NAME had no effect in dog lungs. 3. Pulmonary artery pressure-flow (PPA/Q) relationships were studied over a wide range of flows. In pigs, sheep and human lungs perfused with Krebs-dextran solution, L-NAME increased the PPA/Q slope. This increase was reversed by sodium nitroprusside. In dog lungs L-NAME had no effect. 4. In blood-perfused lungs, the respective responses to L-NAME were similar to those observed with saline. A...
Segmental differences in vasodilatation due to basal NO release in in vivo cat pulmonary vessels
Respiration Physiology, 1999
This study was conducted to examine segmental differences in vasodilatation caused by the basal release of nitric oxide (NO) in the serially connected pulmonary vessels and to estimate the relative contributions of endothelial and neuronal NO synthase (NOS), and inducible NOS to the vasodilatation. Using an X-ray TV system on in vivo cat lungs, we measured internal diameter (ID) changes in resistance (100 -400 mm ID), small conduit (600 -1000 mm) and large conduit (1200-1700 mm) arteries, and veins of the same size. Non-selective NOS inhibitors, L-NAME (30 -50 mg/kg i.v.) and L-NMMA (40-60 mg/kg i.v.), decreased the ID of all vessels studied, although their D-isomers had no effect. The decrease was larger in conduit arteries than in resistance arteries, with maximum response of small conduit arteries (25 9 2%), while venous segments displayed relatively uniform response (10 -12%). L-Arginine completely abolished the ID decrease but hexamethonium bromide and phentolamine had no effect. Selective inhibitors of inducible NOS, L-canavanine (100 mg/kg i.v.) and S-methylisothiourea (10 mg/kg i.v.) did not affect any of the vessels. The data suggest that basal release of NO chiefly derived from endothelial NOS serves to dilate cat pulmonary arteries and veins, particularly small conduit arteries.
Indian journal of experimental biology, 2006
Nitrovasodilators-sodium nitroprusside (SNP; 10(-9)-10(-4) M) and 3-morpholino-sydnonimine (SIN-1; 10(-9)-10(-4) M) produced concentration-dependent relaxation of the fourth generation sheep pulmonary artery, preconstricted with 5-hydroxytryptamine (1 microM). Oxidizing agents [oxidized glutathione (GSSG, 1 mM) and CuSO4 (5 and 20 microM)] and reducing agents [dithiothreitol (DTT, 0.1 mM), ascorbic acid (1 mM) and reduced glutathione (GSH, 1 mM)] caused opposite effects on nitric oxide (NO)-induced vasodilation in the artery. Ascorbic acid and GSH potentiated the NO responses, while GSSG and CuSO4 inhibited relaxation caused by the nitrovasodilators. DTT, however, reduced the relaxant potency and efficacy of SNP and SIN-1. Pretreatment of the pulmonary artery strips with DTT (0.1 mM) inhibited SNP (10 microM)-induced Na(+)-K(+)-ATPase activity, while ascorbic acid (1 mM) and GSH (1 mM) had no effect either on basal or SNP (10 microM)-stimulated 86Rb uptake, an index of Na(+)-K(+)-AT...