The start of the amyloidogenic pathway in Alzheimer’s disease (AD) begins with the deposition of the Aβ₁₋₄₂ peptide surrounded by astrocytes. High levels of arginine and low amounts of neuronal nitric oxide synthase (nNOS) are associated with AD. These astrocytes store reserve arginine that is eventually metabolized by nNOS, within the vicinity of the Aβ₁₋₄₂ peptide. We propose the existence of an association vs. dissociation equilibrium between Aβ and nNOS such that nNOS is an amyloidogenic catalyst for fibrils. When Aβ binds to nNOS, it inhibits the activity of the enzyme (association phase). However when the amyloid peptide dissociates into a form that can no longer bind, later deduced as a fibril, the activity is restored. Thus, the interaction of Aβ with nNOS could serve to regulate the interaction between nNOS and arginine by restoring activity of the enzyme but at the same time promoting fibrillogenesis. Given this event occurring with the neuron, both nNOS and amyloid can serve as a biomarker for the early onset of AD. The enzyme nNOS catalyzed the formation of fibrils in the presence of Aβ peptides, while Ag nps were shown to reverse the fibril formation from Aβ peptides more so than Au and curcumin either through electrostatic or π-π stacking (aromatic) influences. Our studies have shown that the fragments of Aβ₁₋₄₂ i.e. the pentapeptide (Aβ₁₇₋₂₁) and the three glycine zipper peptides (Aβ₂₅₋₂₉, Aβ₂₉₋₃₃, Aβ₃₃₋₃₇) and the full length glycine zipper stretch (Aβ₂₅₋₃₇) all inhibited nNOS activity to varying degrees. The peptides Aβ₁₇₋₂₁ and Aβ₂₉₋₃₃ with their respective Ki values of 5.1 μM and 7.5 μM inhibited the enzyme the most. The Ki values for reversed sequenced peptides (Aβ₁₇₋₂₁r and Aβ₂₉₋₃₃r) were two fold greater than that of the original peptides while the Ki values for the polar forms (Aβ₁₇₋₂₁p and Aβ₂₉₋₃₃p) were between 3-4 fold greater than that of the original peptides. It was also found that Ag nps (Ki = 0.12 μM) inhibited the activity of nNOS the most compared to Au nps; (Ki = 0.15 μM) and curcumin (Ki = 0.25 μM). At 298K, all the ligands bound at a single site on the enzyme (n=1) and a single Trp residue (θ =1), (later identified as Trp678) was made available on the enzyme surface for quenching by the ligands. Increasing the temperature from 298K-313K, increased the value of Ksv and pointed to a dynamic quenching mechanism for Aβ peptides, nps and curcumin interaction with nNOS. The positive signs for entropy and enthalpy for all Aβ peptides nps and curcumin pointed to hydrophobic–hydrophobic interaction with the enzyme. The fact that Kd increased with temperature emphasized the endothermic nature of the binding reaction and the requirement of thermal energy to aid in diffusion of the ligand to the active site. It was concluded that the binding reaction between the ligands and nNOS was non-spontaneous and endothermic at low temperatures (+ΔG) but spontaneous at high temperatures (-ΔG). The two amino acids Tyr706 and Trp678 moved from their original positions, subject to ligand binding. Trp678 moved a minimum distance of 5 Å toward the heme while Tyr706 moved a maximum distance of 14 Å away from the heme. AutoDock 4.2 was a valuable tool in monitoring the distance of Trp678 within the enzyme interior and fluorescence resonance energy transfer (FRET) was efficient in monitoring the distance moved by Trp residues on the enzyme surface.

The importance of sensing Nitric Oxide (NO) in physiology and medicine has led us to explore the reactivity of NO with organometallic Re dyes. Rhenium complexes were synthesized with the ability to react with NO and sense it under physiological conditions. Fluorescent 1,10-phenantroline complexes (phen)Re(PPh3)(CO)2OSO2CF3 (1) and (phen)Re(CH3CN)(CO)2OSO2CF3 (3) can sense NO in the range of 10 - 150 mM showing a decrease in fluorescence response at 514 nm and 532 nm respectively, upon NO-donor addition (lexc = 360 nm). (phen)Re(THF)(CO)2OSO2CF3 (2) showed a ratiometric response with a decrease in fluorescence intensity at 585 nm and an increase at 445 nm. These complexes were characterized by FT-IR, 1H-NMR, 13C-NMR, and 19F‑NMR. The quantum yields (F) and lifetimes (t) were also determined. On the basis of 19F‑NMR and 1H-NMR spectroscopic evidence, the proposed mechanism of action involves dissociation of CF3SO3- (abbreviated as OTf-) together with PPh3, (for 1), THF (for 2), or CH3CN (for 3). Fluorescence microscopy showed that 1 permeates through the cell membrane of rat aortic endothelial cells (RAOEC) and 2 gives increase in cell fluorescence response at 450 nm when exogenous NO is added to RAOEC. The Re complexes of dppz (dppz = 2,2’-dipyrido[3,2-a:2,3’-c]phenazine) (dppz)Re(THF)(CO)2OSO2CF3 (A2) and (dppz)Re(CH3CN)(CO)2OSO2CF3) (A3) were synthesized using the same methods as for complexes 1 and 3. Even though the dppz complexes exhibited similar behavior than the phenanthroline analogs, the signal changes were small and the results were inconclusive. The a-Diimine Re complexes of Xy-DAD (XyDAD = 1,4-bis-[2,6-dimethylphenyl]-1,4-diazo-1,3-butadiene) (Xy-DAD)Re(THF)(CO)2OSO2CF3 (8) and (Xy-DAD)Re(CH3CN)(CO)2OSO2CF3 (9) showed reactivity with NO and CN- with a response in the visible range of the absorption spectrum. These diazadiene (DAD) complexes showed decreased reactivity with NO and CN- in the presence of oxidants. The i-PrDAD complexes (i-PrDAD = 1,4‑bis-[2,6-diisopropylphenyl]-1,4-diazo-1,3-butadiene) (i‑Pr‑DAD)Re(THF)(CO)2OTf (10) and (i‑Pr‑DAD)Re(CH3CN)(CO)2OTf (11) exhibited similar behavior with the Xy-DAD analogs, but the spectral changes were much smaller and the results were inconclusive. The ESI-MS Mass Spectrometry studies of the phenanthroline complexes 1, and 2, after reaction with NO-donor showed that 1 and 2 react with NO to give [Re(CO)2(NO)2S2]+ species, while (phen)Re(CO)3Cl and (phen)Re(CO)3OSO2CF3 do not show any metal-NO containing products, which is consistent with the fluorescence studies.

Activation of inducible nitric oxide synthase (iNOS) and oxidative stress have been shown to be associated with compromised cardiovascular function in streptozotocin (STZ)-induced type 1 diabetes. The aim of the project is to investigate cardiovascular abnormalities in a rat model of type 2 diabetes (Zucker diabetes fatty or ZDF rats) and two models of metabolic syndrome (fructose-fed rats and Zucker obese rats), and to provide direct evidence linking iNOS and oxidative stress to abnormal cardiovascular function in these disorders. Blood pressure, cardiac contractility, cardiac index, regional flow, vascular resistance and venous tone were measured in diseased as well as normal rats. Biochemical analyses such as activities of iNOS, immunostaining of iNOS and western-blot analysis of iNOS in the heart tissue were carried out. The results showed that cardiac contractile response to dobutamine was compromised in the ZDF rats, and this was associated with increased myocardial protein expression as well as activity of iNOS. The formation of peroxynitrite was increased in the heart tissue of the ZDF rats. Selective inhibition of iNOS by 1400W (N-3-aminomethyl-benzyl-acetamidine) did not alter responses to dobutamine in the control rats, but augmented the contractile effects of dobutamine in the diabetic rats. The regional blood flow was altered in the ZDF rats, and iNOS played a negligible role in regulating regional flow in the ZDF rats. Although venous response to noradrenaline was also altered in the Zucker obese rats, NOS may not be involved in venous tone regulation. Anti-oxidative treatment with N-acetylcysteine inhibited the development of insulin resistance, blood pressure elevation and the increase of 8-isoprostane formation in the fructose-fed rats. We conclude that heart function is compromised and regional blood flow is altered in the ZDF rats. Activation of iNOS plays an important role in suppressing heart dysfunction but does not affect regional blood flow. In Zucker obese rats with metabolic syndrome, iNOS may not be involved in changes of venous function. Oxidative stress is associated with both abnormality of heart dysfunction in type 2 diabetes (by formation of peroxynitrite due to iNOS activation) and development of hypertension and insulin resistance in metabolic syndrome. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

High salt intake contributes to the development of hypertension in salt-sensitive humans and animals and the mechanistic causes are poorly understood. In Dahl salt-sensitive (S) but not salt-resistant (R) rats, high salt diet increases cerebrospinal fluid (CSF) [Na+] and activates an aldosterone-mineralocorticoid receptor-epithelial sodium channel-endogenous ouabain (MR-ENaC-EO) neuromodulatory pathway in the brain that enhances the activity of sympatho-excitatory angiotensinergic and glutamatergic pathways, leading to an increase in sympathetic nerve activity (SNA) and blood pressure (BP). We hypothesize that high salt diet in Dahl S rats enhances Ang II release in the paraventricular nucleus (PVN), causing a decrease in local nitric oxide (NO) action and an increase in local glutamate release thereby elevating SNA, BP and heart rate (HR). The present study evaluated the effects of agonists or blockers of MR, ENaC, EO, nitric oxide synthase (NOS) or glutamate and AT1-receptors on the BP and HR responses to acute infusions of Na+ rich aCSF, intracerebroventricularly (icv), or in the PVN of Dahl S, R or Wistar rats or to high salt diet in Dahl S and R rats. In Wistar rats, aldosterone in the PVN enhanced the BP and HR responses to infusion of Na+ rich aCSF in the PVN, but not in the CSF, and only the enhancement was prevented by blockers of MR, ENaC and EO in the PVN. AT1-receptor blockers in the PVN fully blocked the enhancement by aldosterone and the responses to infusion of Na+ rich aCSF icv, or in the PVN. Na+ rich aCSF in the PVN caused larger increases in BP and HR in Dahl S vs. R rats and the responses to Na+ were fully blocked by an AT1-receptor blocker in the PVN. BP and HR responses to a NOS blocker in the PVN were the same, but L-NAME enhanced Na+ effects more in Dahl R than S rats. High salt diet attenuated increases in BP from L-NAME in the PVN of Dahl S but not R rats. AT1 and glutamate receptor blockers candesartan and kynurenate in the PVN decreased BP in Dahl S but not R rats on high salt diet. At the peak BP response to candesartan, kynurenate in the PVN further decreased BP whereas candesartan did not further decrease BP at the peak BP response to kynurenate. Our findings indicate that both an acute increase in CSF [Na+] and high salt intake in Dahl S rats increases AT1-receptor activation and decreases NO action in the PVN thereby contributing to the pressor responses to Na+ and presumably, to dietary salt-induced hypertension. The increased BP response to AT1-receptor activation in the PVN of Dahl S is mediated by enhanced local glutamate receptor activation. An MR-ENaC-EO pathway in the PVN can be functionally active and further studies need to assess its role in Dahl S rats on high salt intake.

Angiogenic cell therapy is currently being developed as a treatment for coronary artery disease (CAD); however, endothelial dysfunction (ED), commonly found in patients with CAD, impairs the ability for revascularization to occur. We hypothesized that culture on a collagen matrix will improve survival and function of circulating progenitor cells (CPCs) isolated from a mouse model of ED. Overall, ED decreased the expression of endothelial markers in CPCs and impaired their function, compared to normal mice. Culture of CPCs from ED mice on collagen was able to increase cell marker expression, and improve migration and adhesion potential, compared to CPCs on fibronectin. Nitric oxide production was reduced for CPCs on collagen for the ED group; however, CPCs on collagen had better viability under conditions of serum deprivation and hypoxia, compared to fibronectin. This study suggests that a collagen matrix may improve the function of therapeutic CPCs that have been exposed to ED.

La pneumopathie interstitielle (PI) est devenue la principale cause de décès de la sclérodermie systémique (ScS). Au cours de PI, l’activation immunitaire déclenche une forte production du monoxyde d’azote (NO) et l’augmentation de la concentration de NO dans l’air expiré des patients atteints de ScS avec PI suggère que cette méthode pourrait détecter précocement l’alvéolite, afin de traiter à temps la PI pour éviter son évolution vers la fibrose pulmonaire. En utilisant le modèle à deux compartiments séparant le NO alvéolaire (CANO) du NO bronchique, nous avons montré que la CANO est : (1) augmentée chez les patients atteints de ScS comparativement aux volontaires sains; (2) associée à l’alvéolite et (3) corrélée à la sévérité de la PI. De plus, une valeur de CANO = 10,8 ppb permettait d’affirmer la présence de la PI et une valeur = 3,8 ppb, d’écarter l’existence d’une PI avec une valeur prédictive= 95%. Le modèle bi-compartimenté néglige la distribution arborisée des voies aériennes et la diffusion axiale du NO, que prend en compte le nouveau « modèle de la trompette ». Les résultats de CANO des 2 méthodes sont comparables (rho=0,98, p<0.001). Enfin, La capacité des sérums à induire la prolifération des fibroblastes pulmonaires et sa conversion en myofibroblaste est augmentée chez les patients atteints de ScS avec une CANO > 5ppb par rapport à celle des patients atteints de ScS qui ont une CANO = 5 ppb et à celle des volontaires sains. Nos résultats suggèrent une relation possible entre l’inflammation alvéolaire et la fibrose pulmonaire au cours de la ScS / Interstitial lung disease (ILD) has become the main cause of death in systemic sclerosis (SSc). In ILD, immune activation leads to strong nitric oxide (NO) output by inducible NO synthase. Increased the whole fractional rate of NO in exhaled air has been reported in SSc patients with ILD and suggested that exhaled NO can be an accurate none-invasive marker of early alveolar inflammation in order to initiate in time treatment. The two compartment-model method partitioned exhaled NO into alveolar concentration (CANO) and conducting airway flux, We hypothesized that overproduction of NO in the lung eventually leads to ILD in SSc. We have found that CANO is significantly increased in SSc patients as compared with healthy controls. We have also demonstrated that high levels of CANO were related to alveolitis and the severity of ILD in SSc. Moreover, we have found that ILD could be ruled in (positive predictive value > 95%) when CANO = 10.8 ppb, and ruled out when CANO values = 3.8 ppb (negative predictive value > 95%). The two-compartment model neglected the trumpet shape of airway tree and the axial diffusion of NO that the advanced “trumpet model” takes account. We have found that CANO levels assessed by the two models were comparable (rho=0,98, p<0.001). Finally, we have found that the serum ability to induce lung fibroblast proliferation and myofibroblast transition was increased in SSc patients with high levels of CANO (>5ppb) as compared to SSc patients with low levels of CANO (=5ppb) and healthy controls. Our findings suggest a possible link between alveolar inflammation, and lung fibrosis in SSc. 1624 caractères avec espace

Many complications associated with heart surgery are due to the negative effects of extracorporeal circulation (ECC). Some of these complications may be attributed to ECC-induced activation of inflammation and coagulation pathways. The inflammatory reaction may be caused by the interaction of blood components with air and the artificial surfaces of the ECC, from substances produced due to ischaemia-reperfusion injury of the heart and lungs, and from increased release of endotoxin from ischemic intestines. Staphylococcus aureus (S. aureus) infections are the leading cause of respiratory, skin and soft tissue, and bloodstream infections. Nitric oxide (NO) is a gaseous signaling molecule involved in many physiological and pathological processes. The role of NO in infection and inflammation is complex. NO may contribute to morbidity by acting as a vasodilator, myocardial depressant, and cytotoxic mediator. On the other hand, NO may have a salutary role through microvascular, cytoprotective, immunoregulatory, and antimicrobial properties. A simulated extracorporeal circulation (SECC) model is a closed circuit, including a roller pump, an oxygenator, a venous reservoir and polyvinyl chloride (PVC) tubing, where human blood is circulated. The SECC model allows studies of the blood and its components, without any influence from other organ systems. The aim of this work was to investigate NO effects during SECC and in S. aureus infection. Study I. Human blood was circulated through SECC during 3 hours, and leukocyte granule release was studied. Results indicated that NO addition during SECC is pro-inflammatory by stimulating leukocyte activation and granule release, and has no effect on oxygen free radical production and interleukin release. Study II. Investigating the effect of NO on S. aureus growth in whole blood during 180 min SECC, results showed a 6.2 fold growth in the presence of NO. Results indicated that by stimulating the expression of inducible lactate dehydrogenase, specific to S. aureus, NO may improve S. aureus resistance to oxidative stress, giving the pathogen a survival advantage. Study III. In an in vitro system of SECC, we measured glyceryl trinitrate (GTN) induced changes in leukocyte activation in whole blood caused by S. aureus infestation, as well as the effect of GTN on S. aureus growth. Results indicated that GTN does not affect S. aureus growth during SECC and has no effect on SECC-induced leukocyte activation. Study IV. Whole blood concentrations of selected leukocyte adhesion molecules, complement system components and myeloperoxidase  were measured in an in vitro system of SECC. Results indicated that SECC induces the increased expression of some leukocyte markers and that GTN addition significantly reduces the expression of some leukocyte activation markers.

Orientador: Stephen Hyslo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-07T09:47:37Z (GMT). No. of bitstreams: 1 Tarsitano_ChristianeAparecidaBadin_D.pdf: 24957423 bytes, checksum: 94d8809a19e27ce5d2957100482d3d27 (MD5) Previous issue date: 2006 / Resumo: óxido nítrico (NO), um co-produto do metabolismo do aminoácido Larginina para L-citrulina pela NO sintase (NOS), exerce importantes funções no controle do tôno vascular, no processo inflamatório, e na modulação da expressão gênica e atividade enzimática de diversas enzimas, tais como citocromos P-450 e NOS. A inibição crônica da biossíntese de NO por NW-nitro-L-argininemetil éster (L-NAME) leva à hipertensão e produz alterações morfológicas que incluem hipertrofia e remodelamento vascular, efeitos estes que são revertidos por inibidores da enzima conversora de angiotensina I (ECA) e antagonistas dos receptores AT1 de angiotensina 11. O NO exerce papel fundamental na hemodinâmica e função celular do fígado, e pode regular a atividade dos citocromos P450 monooxigenases que são importantes na biotransformação de substâncias endógenas e exógenas. Neste trabalho, examinamos a influência do tratamento com L-NAME sobre a morfologia hepática, o conteúdo de glicogênio, colesterole triglicérides,e a atividadee expressãodas isoformasCYP1A1/2, CYP 281/2, CYP2C11 e CYP2E1de citocromoP450.No tratamentoagudo estudamos também a expressão de duas metaloproteinases de matriz (MMP-2 e MPP-9). Ratos Wistar machos foram tratados com L-NAME (20 mg/rato/dia, administrado na água de beber) por quarto e oito dias (tratamento agudo) e duas, quatro e oito semanas (tratamento crônico) e os fígados foram removidos para análise. A indução enzimática foi realizada tratando-se os ratos com fenobarbital (para induzir CYP2B1/2), p-naphthoflavone (para induzir CYP1A1/2) (80 mg/kg/dia, Lp., 4 d) ou pirazole (200 mg/kg/dia, Lp., 2 d) (para induzir CYP2E1). O tratamento com L-NAME elevou significativamente a pressão sangüínea e esta foi revertida pelo tratamento concomitante com enalapril (25 mg/kg/dia, p.o., inibidor da ECA) ou losartan (30 mg/kg/dia, p.O.,antagonista dos receptores AT1). L-NAME causou hipertrofia vascular em artérias hepáticas, com depósito de colágeno perivascular e fibrose intersticial. Houve também um aumento significativo no conteúdo de glicogênio hepático. Todas estas alterações foram completamente revertidas por enalapril ou losartan. O tratamento com L-NAME não alterou o conteúdo de colesterol e triglicérides hepáticos, e não afetou as atividades basais e induzidas ou a expressão das isoformas de citocromo P450. O tratamento agudo com LNAME aumentou a expressão de MMP-2 e MMP-9 na parede vascular e em células inflamatórias (Ieucócitos, macrófagos). Esses resultados mostram que o tratamento agudo e crônico com L-NAME produz alterações morfológicas na vasculatura hepática e aumenta o conteúdo hepático de glicogênio, sem porém alterar o metabolismo de lípides ou a atividade e expressão de citocromos P450. A ausência de um efeito sobre os citocromos P450 indica que estas enzimas, não são influenciadas por níveis baixos de NO. Já a capacidade do enalapril e losartan em proteger contra as alterações morfológicas e o aumento de glicogênio indica um papel importante para o sistema renina-angiotensina nestas respostas / Abstract: Nitric oxide (NO), a co-product of the metabolism of L-arginine to L-citrulline by NO synthases (NOS), has an important role in regulating vascular tone, inflammatory responses, and the gene expression and enzymatic activity of various proteins, including cytochrome P450 and NOS. The chronic inhibition of NOS by Nffi-nitro-L-arginine methyl ester (L-NAME) produces sustained arterial hypertension and morphological alterations that include arterial wall hypertrophy and vascular remodeling. These changes can be prevented by concomitant treatment with angiotensin-converting enzyme (ACE) inhibitors and angiotensin 11 AT1 receptor antagonists. NO is an important modulator in the hepatic vasculature and of hepatic cell function, and may regulate the activity of cytochrome P450 monooxygenases involved in the biotransformation of endogenous and exogeous substances. In this work, we examined the influence of L-NAME on rat liver morphology, hepatic glycogen, cholesterol and triglyceride content, and the activities and expression of the cytochrome P450 isoforms CYP1A1/2, CYP2B1/2, CYP2C11 and CYP2E1. We also examined the expression of two matrix metalloproteinases (MMP-2 and MPP-9) after short-term treament with L-NAME. Male Wistar rats were treated with L-NAME (20 mg/ratlday, administered in the drinking water) for four and eight days (short-term treatment) and two, four and eight weeks (chronic treatment) and the livers were then removed for analysis. Enzymatic induction was produced by treating rats with phenobarbital (to induce CYP2B1/2), ~-naphthoflavone (to induce CYP1A1/2) (80 mg/kg/day each, i.p., 4 d) or pyrazole (200 mg/kg/day, i.p., 2 d) (to induce CYP2E1). Treatment with LNAME significantly elevated the blood pressure and this was reversed by concomitant treatment with enalapril (25 mg/kg/day, p.o., ACE inhibitor) or losartan (30 mg/kg/day, p.o., angiotensin II AT1 receptor antagonist). L-NAME caused vascular hypertrophy in hepatic arteries, with perivascular and interstitial fibrosis involving collagen deposition. There was also a significant increase in the hepatic glycogen content. Ali of these changes were completely reversed by concomitant treatment with enalapril or losartan. L-NAME had no effect on the hepatic cholesterol and triglyceride content, nor did it affect the basal or drug-induced activities and protein expression of the cytochrome P450 isoforms. Short-term treatment with L-NAME enhanced the expression of MMP-2 and MMP-9 in vessel walls and inflammatory cells (mast cells, macrophages). These results show that acute or chronic treatment with L-NAME produces morphological alterations in the hepatic vasculature and increases the hepatic glycogen content without affecting lipid metabolism or the activity or expression of cytochrome P450 isoforms. The lack of effect on cytochrome P450 activities and expression indicates that these enzymes are not significantly influenced by low levels of NO. In contrast, the ability of enalapril and losartan to prevent the morphological alterations and the increase in hepatic glycogen indicates an important role for the renin-antiogensin system in these responses / Doutorado / Histologia / Doutor em Biologia Celular e Estrutural

Orientador: Gilberto de Nucci / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-07T12:13:37Z (GMT). No. of bitstreams: 1 Baracat_JulianaSignori_D.pdf: 5461737 bytes, checksum: 0ff83b88634432535b68af4042a52fff (MD5) Previous issue date: 2006 / Doutorado / Farmacologia / Doutor em Ciências Médicas

Orientador: Gilberto de Nucci / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-07T17:06:06Z (GMT). No. of bitstreams: 1 Okuyama_CristinaEunice_D.pdf: 791888 bytes, checksum: 44bf756719cf0cdc26ab70b220532e28 (MD5) Previous issue date: 2006 / Resumo: Compostos farmacológicos que liberam óxido nítrico (NO) têm sido utilizados para avaliar o amplo papel do NO na fisiopatologia e terapêutica de diversas doenças. Estudos demonstram que a deficiência de NO está envolvida com a gênese e evolução de diversos estágios de doenças como, por exemplo, a hipertensão. Deste modo, a adição de uma molécula de NO em drogas previamente estudadas vem sendo praticada por diversos pesquisadores na última década. Estes pesquisadores buscam associar as propriedades farmacológicas de cada droga com as atividades proporcionadas pelo NO exógeno. No presente trabalho, comparamos a farmacocinética e a farmacodinâmica do enalapril com as de um nitro-derivado do enalapril (NCX899), em Beagles machos não anestesiados. Os efeitos do enalapril e NCX899 na hipertensão arterial, bradicardia e vasoconstrição periférica induzida pela inibição aguda da síntese de NO em cães anestesiados também foram investigados. Na avaliação farmacocinética, os cães receberam NCX899 (4 µmol/Kg) ou Enalapril (4 µmol/Kg) pela via intravenosa. Em seguida, as concentrações plasmáticas dos analitos e metabólitos foram quantificadas pelo método de cromatografia líquida de alta eficiência, acoplada à espectrometria de massa (LCMS- MS). No grupo NCX899, a área sob a curva (ASC0-24h) foi 29,18 ± 4,72, 229,37 ± 51,32 e 5159,23 ± 514,88 µgh/l para os analitos nitro-enalapril, enalapril e enalaprilato, respectivamente. No grupo Enalapril, a ASC0-24h foi de 704,53 ± 158,86 e 4149,27 ± 847,30 µgh/l para os analitos enalapril e enalaprilato, respectivamente. As análises estatísticas entre os grupos demonstraram uma diferença significativa para o analito enalapril, mas não para o analito enalaprilato, o metabólito ativo. Entretanto, o NCX899 e o Enalapril foram efetivos de maneira semelhante na inibição da atividade da enzima conversora de angiotensina sérica. Em cães anestesiados, a administração intravenosa do inibidor da síntese de NO, o N?-nitro-L-arginina metil éster (L-NAME; 0,1-10 mg/kg), elevou significativamente a pressão arterial e causou bradicardia. O composto NCX899 atenuou significativamente a hipertensão arterial, bradicardia e vasoconstrição periférica, enquanto o Enalapril não apresentou efeito significativo. Além disso, nossos estudos também demonstraram que o NCX899 pode atuar não só como anti-hipertensivo, mas também auxiliar na inibição da agregação plaquetária. Assim, concluímos que o nitro-derivado do enalapril (NCX899) apresenta uma relação farmacocinética/farmacodinâmica similar ao composto enalapril. No entanto, ao contrário do Enalapril, o NCX899 apresenta um efeito protetor nas alterações cardiovasculares induzidas pela inibição aguda de NO / Abstract: Pharmacological compounds that release nitric oxide (NO) have been useful tools for evaluating the broad role of NO in physiopathology and therapeutics of several diseases. Studies show that lack of NO can cause several diseases such as hypertension. Thus, the addition of a NO molecule in drugs previously studied has been reported by some researchers in the last decade. They look for the combination of the pharmacologic properties of each drug, plus exogenous NO properties. This work has compared the pharmacokinetics and pharmacodynamics of enalapril and a NO-releasing enalapril molecule (NCX899) in conscious male Beagles. The effects of both enalapril and NCX899 in the arterial hypertension, bradycardia and peripheral vasoconstriction induced by acute NO inhibition in anesthetized dogs have also been investigated. In the pharmacokinetic evaluation, dogs received either NCX899 (4 µmol/Kg) or Enalapril (4 µmol/Kg) intravenously. Later, the plasma concentrations of the analytes and metabolites were quantified by liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS). In the NCX899 group, the area under time-course curve (AUC0-24h) was 29.18 ± 4.72, 229.37 ± 51.32 and 5159.23 ± 514.88 µgh/l for the nitro-enalapril, enalapril and enalaprilat analytes, respectively. In the Enalapril group, the AUC0-24h was 704.53 ± 158.86 and 4149.27 ± 847.30 µgh/l for the enalapril and enalaprilat analytes, respectively. The statistical analysis between both groups showed a significant difference for the enalapril analyte, but not for enalaprilat, the active metabolite. Moreover, NCX899 and Enalapril were equally effective on inhibiting the activity of serum angiotensin-converting enzyme. In anesthetized dogs, intravenous administration of the NO synthase (NOS) inhibitor N?-nitro-L-arginine methyl ester (L-NAME; 0.1-10 mg/kg) significantly elevated arterial blood pressure with concomitant bradycardia. The compound NCX899 significantly attenuated arterial hypertension, bradycardia and peripheral vasoconstriction, whereas Enalapril had no significant effect. In addition, our work showed that NCX899 also has properties of inhibiting the activity of platelets aggregation. In conclusion, our results showed that the NO-releasing derivative of enalapril NCX899 presents a pharmacokinetic / pharmacodynamic relationship similar to the enalapril compound. Moreover, different from Enalapril, NCX899 presented protective effect in the cardiovascular alterations induced by acute NOS inhibition / Doutorado / Doutor em Farmacologia