Effects of NO/cGMP inhibitors in a rat model of anaphylactoid shock

Anaphylactic shock can be defined as an acute syndrome, and it is the most severe clinical manifestation of allergic diseases. Anaphylactoid reactions are similar to anaphylactic events but differ in the pathophysiological mechanism. Nitric oxide (NO) inhibitors during anaphylaxis suggest that NO might decrease the signs and symptoms of anaphylaxis but exacerbate associated vasodilation. Therefore, blocking the effects of NO on vascular smooth muscle by inhibiting the guanylate cyclase (GC) would be a reasonable strategy. This study aimed to investigate the effects of NO/cGMP pathway inhibitors methylene blue (MB), Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME), and indigo carmine (IC) in shock induced by compound 48/80 (C48/80) in rats. The effect was assessed by invasive blood pressure measurement. Shock was initiated by C48/80 intravenous bolus injection 5 min before (prophylactic) or after (treatment) the administration of the inhibitors MB (3 mg/kg), L-NAME (1 mg/kg), and IC (3 mg/kg). Of the groups that received drugs as prophylaxis for shock, only the IC group did not present the final systolic blood pressure (SBP) better than the C48/80 group. Regarding shock treatment with the drugs tested, all groups had the final SBP similar to the C48/80group. Altogether, our results suggested that inhibition of GC and NO synthase in NO production pathway was not sufficient to revert hypotension or significantly improve survival.

Chronic aerobic exercise associated to low-dose L-NAME improves contractility without changing calcium handling in rat cardiomyocytes

Nitric oxide (NO) inhibition by high-dose NG-nitro-L-arginine methyl ester (L-NAME) is associated with several detrimental effects on the cardiovascular system. However, low-dose L-NAME increases NO synthesis, which in turn induces physiological cardiovascular benefits, probably by activating a protective negative feedback mechanism. Aerobic exercise, likewise, improves several cardiovascular functions in healthy hearts, but its effects are not known when chronically associated with low-dose L-NAME. Thus, we tested whether the association between low-dose L-NAME administration and chronic aerobic exercise promotes beneficial effects to the cardiovascular system, evaluating the cardiac remodeling process. Male Wistar rats were randomly assigned to control (C), L-NAME (L), chronic aerobic exercise (Ex), and chronic aerobic exercise associated to L-NAME (ExL). Aerobic training was performed with progressive intensity for 12 weeks; L-NAME (1.5 mg·kg-1·day-1) was administered by orogastric gavage. Low-dose L-NAME alone did not change systolic blood pressure (SBP), but ExL significantly increased SBP at week 8 with normalization after 12 weeks. Furthermore, ExL promoted the elevation of left ventricle (LV) end-diastolic pressure without the presence of cardiac hypertrophy and fibrosis. Time to 50% shortening and relaxation were reduced in ExL, suggesting a cardiomyocyte contractile improvement. In addition, the time to 50% Ca2+ peak was increased without alterations in Ca2+ amplitude and time to 50% Ca2+ decay. In conclusion, the association of chronic aerobic exercise and low-dose L-NAME prevented cardiac pathological remodeling and induced cardiomyocyte contractile function improvement; however, it did not alter myocyte affinity and sensitivity to intracellular Ca2+ handling.

Nitric oxide modulates ATP-evoked currents in mouse Leydig cells

Testosterone synthesis within Leydig cells is a calcium-dependent process. Intracellular calcium levels are regulated by different processes including ATP-activated P2X purinergic receptors, T-type Ca2+ channels modulated by the luteinizing hormone, and intracellular calcium storages recruited by a calcium-induced calcium release mechanism. On the other hand, nitric oxide (NO) is reported to have an inhibitory role in testosterone production. Based on these observations, we investigated the interaction between the purinergic and nitrergic systems in Leydig cells of adult mice. For this purpose, we recorded ATP-evoked currents in isolated Leydig cells using the whole cell patch clamp technique after treatment with L-NAME (300 μM and 1 mM), L-arginine (10, 100, 300, and 500 μM), ODQ (300 μM), and 8-Br-cGMP (100 μM). Our results show that NO produced by Leydig cells in basal conditions is insufficient to change the ATP-evoked currents and that extra NO provided by adding 300 μM L-arginine positively modulates the current through a mechanism involving the NO/cGMP signaling pathway. Thus, we report an interaction between the nitrergic and purinergic systems in Leydig cells and suggest that Ca2+ entry via the purinergic receptors can be regulated by NO.

Effects of chronic administration of tamsulosin and tadalafil, alone or in combination, in rats with bladder outlet obstruction induced by chronic nitric oxide deficiency

Purpose The aim of this study was to define if tadalafil causes detrusor muscle impairment and to observe the effect of combination of tadalafil with tamsulosin on the lower urinary tract of rats with bladder outlet obstruction (BOO) induced by chronic nitric oxide deficiency. Materials and Methods Thirty-one male rats were randomized to following groups: 1 - control; 2 - L-Nitroarginine methyl ester (L-NAME); 3 - Tamsulosin + L-NAME, 4 Tadalafil+L-NAME; and 5 - Tamsulosin + Tadalafil + L-NAME. At the end of the treatment period (30 days), all animals were submitted to urodynamic study. Results The administration of L-NAME increased the number of non-voiding contractions (NVC) (1.04 ± 0.22), volume threshold (VT) (1.86 ± 0.35), and micturition cycle (MC) (1.34 ± 0.11) compared with control (0.52 ± 0.06, 0.62 ± 0.06, and 0.67 ± 0.30), respectively. The administration of tamsulosin reduced the number of NVC (0.57 ± 0.42) and VT (0.76 ± 0.24 ) compared with L-NAME group. Co-treatment with tadalafil decreased the number of VT (0.85 ± 0.53) and MC (0.76 ± 0.22) compared with L-NAME group. The combination of tamsulosin with tadalafil improved the number of NVC (0.56 ± 0.18), VT (0.97 ± 0.52) and MC (0.68 ± 0.30) compared with L-NAME group. Conclusion In rats with BOO induced by chronic nitric oxide deficiency, tadalafil did not cause impairment in detrusor muscle and seems to have an addictive effect to tamsulosin because the combination decreased non voiding contractions as well the number of micturition cycles. .

Effect of acute administration of sildenafil to rats with detrusor overactivity induced by chronic deficiency of nitric oxide

Purpose Recently, the effect of phosphodiesterase inhibitors (PDE5i) in the lower urinary tract symptoms (LUTS) associated to benign prostatic hyperplasia have been studied thoroughly. However, it remains unclear how the PDE5i improve LUTS. Therefore, the aim of the present study was to evaluate the potential of acute administration of the PDE5i sildenafil to improve detrusor overactivity (DO) induced by Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME), an nitric oxide sinthase (NOS) inhibitor, in rats. Materials and Methods Twenty-seven MALE adult Wistar Rats were divided into the following groups: (1) control, (2) L-NAME, (3) sildenafil alone, and (4) L-NAME + sildenafil. The NOS blocker L-NAME (20 mg/rat/day) was given in the drinking water. Sildenafil (100µg/kg) was administrated intravenously (i.v.) acutely, diluted in cremophor, propylene glycol and water. All animals underwent to anesthetized cystometograms. Results The chronic and systemic administration of L-NAME markedly increased the number of non voiding contractions (2.62 (± 0.89)), and frequency of micturition (1.97 (± 0.78)), as well increased volume threshold (2.83 mL (± 1.64)) compared with control group, the number of non voiding contractions (1.17 (± 0.75)), frequency of micturition (1.08 (± 0.65)) and volume threshold (1.16 mL (± 0.38)), p < 0.001, p = 0.01, and p = 0.04, respectively. Sildenafil infusion decreased the number of micturition cycles significantly from the baseline to end point (-0.93 (± 0.34)) in nitric oxide (NO) deficient animals compared with sildenafil infusion alone (control) in animals with normal NO level (0.13 (± 0.25)), p = 0.03. Conclusion Systemic reduction of nitric oxide causes detrusor overactivity and acute infusion of sildenafil reduces the number of micturition cycles in chronic NO-deficient rats. .

Inhibition of nitric oxide synthesis for four days induces vascular abnormalities and myocardial infarct areas but not significant arterial hypertension / Inibição da síntese do óxido nítrico durante quatro dias induz anormalidades vasculares e áreas de infarto miocárdico, porém, não induz hipertensão arterial significativa

BACKGROUND: Nitric oxide is an endothelium vasorelaxing factor and at least in some cases is the main cause of arterial hypertension, which is one of the most important risk factors of cardiovascular diseases. In Brazil, cardiovascular diseases are the first cause of mortality, representing about 30% of the total deaths. The L-NAME (Nω-nitro-arginine-methyl-ester) blocks the nitric oxide synthesis necessary to maintain the normal arterial pressure. OBJECTIVE: To study lesions in myocardium due to the inhibition of nitric oxide synthesis during four days (via L-NAME oral administration, concentration: 75 mgs versus 100 mL-1). METHODS: Fourteen normotensive young adults Wistar rats were submitted, during four days, to L-NAME. Six rats were utilized as the Control Group. At day 4 of the experiment, the animals were anesthetized, weighed, and their thoraxes were opened, and the cardiotomy was performed. The hearts were weighed, fixed, and processed using routine methods, and they were sectioned in 3 µm and stained. RESULTS: Abnormalities were observed in the wall of arterial vessels of any dimension, as vascular damage with increasing wall thickness related mainly to proliferation of arterial smooth muscle cell in submitted animals. Proliferation of cells in the intimal layer and its thickening were also observed in small arterial vessels (arteriole). Infarct areas were present. CONCLUSIONS: The present data suggested that inhibition of nitric oxide synthesis for four days induces vascular abnormalities and myocardial infarct areas, but not arterial hypertension.

CONTEXTO: O óxido nítrico é um fator de relaxamento vascular e, pelo menos em certos casos, é a principal causa de hipertensão arterial no ser humano. A hipertensão arterial é um importante fator de risco de doenças cardiovasculares. No Brasil, as doenças cardiovasculares são a primeira causa de mortalidade, representando cerca de 30% do total de óbitos. O L-NAME (Nω-nitro-arginina-metil-éster, Sigma Chemical, St. Louis) bloqueia a síntese do óxido nítrico necessária para a manutenção da pressão arterial normal. OBJETIVO: Estudar as lesões miocárdicas ocorridas por razão da inibição da síntese do óxido nítrico durante quatro dias (por meio da administração oral de L-NAME em concentração de 75 mgs versus 100 mL-1). MÉTODOS:Quatorze ratos Wistar jovens normotensos adultos foram submetidos durante quatro dias ao L-NAME. Seis foram utilizados como Grupo Controle. Aos quatro dias de experimento, os animais foram anestesiados, pesados, os tórax foram abertos e a cardiomiotomia foi efetuada. Os corações foram pesados, fixados e processados usando métodos de rotina e cortados em 3 µm de espessura e corados. RESULTADOS: As anormalidades foram observadas nas paredes arteriais de vasos de todos os calibres, como, por exemplo, o aumento da parede arterial relacionada principalmente à proliferação das células musculares lisas dos animais submetidos ao bloqueio do óxido nítrico. Também foi identificada proliferação das células da túnica íntima e seu espessamento nos vasos arteriais de pequeno calibre (arteríolas). Áreas de infarto estavam presentes. CONCLUSÕES: Os resultados sugerem que a inibição do óxido nítrico durante quatro dias induz anormalidades vasculares e áreas de infarto do miocárdio, contudo, não induz hipertensão arterial.

Effects of Nitric Oxide Synthase Inhibitor on Hindlimb Muscles in Rats with Neuropathic Pain Induced by Unilateral Peripheral Nerve Injury

PURPOSE: The purpose of this study was to examine effects of nitric oxide synthase (NOS) inhibitor on muscle weight and myofibrillar protein content of affected and unaffected hindlimb muscles in rats with neuropathic pain induced by unilateral peripheral nerve injury. METHODS: Neuropathic pain was induced by ligation and cutting of the left L5 spinal nerve. Adult male Sprague-Dawley rats were randomly assigned to one of two groups: The NOSI group (n=19) had NOS inhibitor (L-NAME) injections daily for 14 days, and the Vehicle group (n=20) had vehicle injections daily for 14 days. Withdrawal threshold, body weight, food intake and activity were measured every day. At 15 days all rats were anesthetized and soleus, plantaris and gastrocnemius muscles were dissected from hindlimbs. Muscle weight and myofibrillar protein content of the dissected muscles were determined. RESULTS: The NOSI group showed significant increases as compared to the Vehicle group for body weight at 15 days, muscle weight and myofibrillar protein content of the unaffected soleus and gastrocnemius. The NOSI group demonstrated a higher pain threshold than the vehicle group. CONCLUSION: NOSI for 14 days attenuates unaffected soleus and gastrocnemius muscle atrophy in neuropathic pain model.

Consequences of cerebroventricular insulin injection on renal sodium handling in rats: effect of inhibition of central nitric oxide synthase

In the present study, we investigated the effects of acute intracerebroventricular (icv) insulin administration on central mechanisms regulating urinary sodium excretion in simultaneously centrally NG-nitro-L-arginine methylester (L-NAME)-injected unanesthetized rats. Male Wistar-Hannover rats were randomly assigned to one of five groups: a) icv 0.15 M NaCl-injected rats (control, N = 10), b) icv dose-response (1.26, 12.6 and 126 ng/3 µL) insulin-injected rats (N = 10), c) rats icv injected with 60 µg L-NAME in combination with NaCl (N = 10) or d) with insulin (N = 10), and e) subcutaneously insulin-injected rats (N = 5). Centrally administered insulin produced an increase in urinary output of sodium (NaCl: 855.6 ± 85.1 Ä percent/min; 126 ng insulin: 2055 ± 310.6 Ä percent/min; P = 0.005) and potassium (NaCl: 460.4 ± 100 Ä percent/min; 126 ng insulin: 669.2 ± 60.8 Ä percent/min; P = 0.025). The urinary sodium excretion response to icv 126 ng insulin microinjection was significantly attenuated by combined administration of L-NAME (126 ng insulin: 1935 ± 258.3 Ä percent/min; L-NAME + 126 ng insulin: 582.3 ± 69.6 Ä percent/min; P = 0.01). Insulin-induced natriuresis occurred by increasing post-proximal sodium excretion, despite an unchanged glomerular filtration rate. Although the rationale for decreased urinary sodium excretion induced by combined icv L-NAME and insulin administration is unknown, it is tempting to suggest that perhaps one of the efferent signals triggered by insulin in the CNS may be nitrergic in nature.

Beneficial effects of angiotensin II AT1 blocker on cardiovascular adverse remodeling due to nitric oxide synthesis blockade / Efectos Beneficiosos del Bloqueador AT1 de la Angiotensina II en la Remodelación Cardiovascular Adversa Causada por el Bloqueo de la Síntesis de Óxido Nítrico

Se estudiaron con herramientas morfológicas, los efectos de diferentes dosis de Losartan sobre el remodelamiento cardiovascular, en ratas deficientes en óxido nítrico. 30 ratas Wistar, con 15 semanas de edad, fueron separadas en 6 grupos. control (C), L-NAME (LN), y 4 grupos en que administró LN junto con Losartan, en diferentes dosis (1, 5, 20 y 40 mg/kg/dia). El L-NAME fue administrado durante 9 semanas y la administración de Losartan se inició en la segunda semana de experimentación. Se estudiaron el corazón, la parte torácica de la aorta y la arteria mesentérica craneal, con microscopía de luz y estereología. La presión arterial (PA) aumentó desde la primera semana de administración de L-NAME. El tratamiento con Losartan, en las dosis de 20 y 40 mg/kg/día, fue eficiente para reducir la PA después de la séptima semana de tratamiento. El remodelamiento cardiaco adverso en el grupo LN se caracterizó por intensa fibrosis intersticial, disminución de la microvascularización miocárdica e hipertrofia y consecuente pérdida de cardiomiocitos. La estructura de la pared de la aorta (densidad por área de núcleos de células musculares lisas y densidad de superficie de lamelas), y la relación media/luz de la arteria mesentérica craneal, también fueron muy alteradas por la administración de L-NAME. Sólo en una dosis igual o mayor que 20 mg/kg/día, el Losartan tuvo efecto benéfico tratando estas alteraciones. En conclusión, tanto el corazón como la pared arterial de ratas deficientes en óxido nítrico, presentan un proceso de remodelamiento acentuado, y éste es eficientemente tratado con Losartan en diferentes dosis. La eficiencia del tratamiento con Losartan en el modelo de bloqueo de la síntesis de óxido nítrico se correlaciona con el efecto hipotensor de la droga, principalmente en las dosis más elevadas.

We studied with morphological tools the effects of different doses of Losartan upon the cardiovascular remodeling in nitric oxide deficient rats. At 15 weeks of age, thirty Wistar rats were separated in six groups: control (C), L-NAME (LN), and four groups were LN was given plus Losartan at different doses (1, 5, 20 and 40 mg/kg/day). The L-NAME was given for 9 weeks, the Losartan administration starting on the 2nd week of experiment. We studied the heart, thoracic aorta and superior mesenteric artery with light microscopy and stereology. The blood pressure (BP) increased since the first week of L-NAME administration, the Losartan treatment at doses of 20 and 40 mg/kg/day was efficient to reduce BP after the 7th week of treatment. The cardiac adverse remodeling in the LN group was characterized by intense interstitial fibrosis, impairment of the myocardial microvascularization, cardiomyocyte hypertrophy and consequent loss of cardiomyocytes. The aortic wall structure (density per area of smooth muscle cell nuclei and surface density of lamellae), and the superior mesenteric artery media/lumen ratio were also strongly affected by L-NAME administration. Only in the dose equal or higher than 20 mg/kg/day Losartan showed beneficial effects treating these alterations. In conclusion, both the heart and the arterial wall of NO deficient rats suffer a marked adverse remodeling process that is efficiently treated by a dose-dependent Losartan administration. The efficiency of Losartan treatment in this model of NO synthesis blockade correlates with the hypotensor effect of the drug mainly in the high dose treatment.

Efeito do lipopolissacarídio bacteriano sobre o esvaziamento gástrico de ratos: avaliação do pré-tratamento com Nw-nitro-L-arginine methyl ester (L-NAME) / The effect of bacterial lipopolysaccharide on the gastric emptying of rats: a pretreatment evaluation using Nw-nitro-L-arginine methyl ester (L-NAME) / The effect of bacterial lipopolysaccharide on the gastric emptying of rats: a pretreatment evaluation using Nw-nitro-L-arginine methyl ester (L-NAME)

RACIONAL: Há evidências de que o óxido nítrico participa do mecanismo de retardo do esvaziamento gástrico determinado pelo lipopolissacarídio bacteriano. OBJETIVO: Avaliar o efeito do pré-tratamento com Nw-nitro-L-arginine methyl ester, um inibidor competitivo das óxido nítrico-sintetases, sobre o fenômeno. MATERIAL E MÉTODOS: Utilizaram-se ratos, Wistar, machos, SPF ("specific-pathogen free"), adultos, adaptados às condições do laboratório, que após 24 horas de jejum alimentar foram pré-tratados endovenosamente com veículo (salina) ou Nw-nitro-L-arginine methyl ester nas doses de 0,5, 1, 2,5 e 5 mg/kg. No tratamento, administrou-se endovenosamente veículo (salina) ou lipopolissacarídio (50 µg/kg). O intervalo entre o pré-tratamento e o tratamento foi de 10 minutos, e entre este e a avaliação do esvaziamento gástrico foi de 60 minutos. O esvaziamento gástrico foi avaliado indiretamente através da determinação da retenção gástrica da solução salina marcada com fenol vermelho 10 minutos após administração por via orogástrica. RESULTADOS: Entre os animais pré-tratados com veículo, o tratamento com lipopolissacarídio determinou elevação significativa da retenção gástrica (média = 57 por cento) em relação aos tratados com veículo (38,1 por cento). O pré-tratamento com as diferentes doses de Nw-nitro-L-arginine methyl ester não modificou a retenção gástrica nos animais controles do tratamento. O pré-tratamento com Nw-nitro-L-arginine methyl ester com a dose de 1 mg/kg determinou redução discreta, mas significativa, na retenção gástrica (52 por cento) nos animais tratados com lipopolissacarídio, em relação ao observado naqueles com pré-tratamento e tratamento com veículo (35,9 por cento). Nos animais pré-tratados com 2,5 e 5 mg/kg de Nw-nitro-L-arginine methyl ester e tratados com lipopolissacarídio, houve aumento significante da retenção gástrica (74,7 por cento e 80,5 por cento, respectivamente) em relação aos seus controles pré-tratados com as mesmas doses...

BACKGROUND: There is evidence that nitric oxide plays a role in the decrease in gastric emptying induced by bacterial lipopolysaccharide. AIM: To evaluate the effect of pretreatment with Nw-nitro-L-arginine methyl to ester, one competitive inhibitor of the nitric oxide syntases, on the gastric emptying delay induced by lipopolysaccharide. MATERIAL AND METHODS: Male Wistar rats, SPF, were used after 24 h fast and 1 h-water withdrawn. The pretreatment was done intravenously with vehicle (saline) or Nw-nitro-L-arginine methyl to ester in the doses of 0.5, 1, 2.5 e 5 mg/kg. After 10 min, the animals were treated iv with lipopolysaccharide (50 mg/kg) or received vehicle (saline). The gastric emptying was evaluated 1 h after the lipopolysaccharide administration. A saline solution containing phenol red was used as the test meal. The gastric emptying was indirectly assessed by the determination of percent gastric retention of the test meal 10 min after orogastric administration. RESULTS: The animals pretreated with vehicle and treatment with lipopolysaccharide have significant rise of the gastric retention (average = 57 percent) in comparison with the controls receiving only vehicle (38.1 percent). The pretreatment with the different doses of Nw-nitro-L-arginine methyl to ester did not modify per se the gastric retention in comparison with the animals pretreated with vehicle. Pretreatment with Nw-nitro-L-arginine methyl to ester with the dose of 1 mg/kg determined a discrete but significant reduction in the gastric retention (52 percent) of animals treated with lipopolysaccharide in comparison with vehicle-pretreated rats. Paradoxically, animals pretreated with 2.5 or 5 mg of Nw-nitro-L-arginine methyl to ester/kg followed by treatment with lipopolysaccharide displayed a significantly higher gastric retention (74.7 percent and 80.5 percent, respectively) as compared to their controls, pretreated with the same doses of the inhibitor and treated with vehicle (40.5 percent and...

Pretreatment with N-nitro-L-arginine Methyl Ester Improved Oxygenation After Inhalation of Nitric Oxide in Newborn Piglets with Escherichia coli Pneumonia and Sepsis

We evaluated the effects of a combined therapy of pre-blockade endogenous nitric oxide synthase (NOS) with N-nitro-L-arginine methyl ester (L-NAME) and continuous inhaled NO (iNO) on the gas exchange and hemodynamics of Escherichia coli pneumonia and sepsis in newborn piglets. Seven to ten day old ventilated newborn piglets were randomized into 5 groups: control, E. coli pneumonia control, pneumonia with iNO 10 ppm, pneumonia pre-treated with L-NAME 10 mg/kg, and pneumonia with the combined therapy of L-NAME pretreatment and iNO. E. coli pneumonia was induced via intratracheal instillation of Escherichia coli, which resulted in progressively decreased cardiac index and oxygen tension; increased pulmonary vascular resistance index (PVRI), intrapulmonary shunting, and developed septicemia at the end of 6 hr experiment. iNO ameliorated the progressive hypoxemia and intrapulmonary shunting without affecting the PVRI. Only two of 8 animals with L-NAMEpretreated pneumonia survived. Whereas when iNO was added to infected animals with L-NAME pretreatment, the progressive hypoxemia was abolished as a result of a decrease in intrapulmonary shunting without reverse of the high PVRI and systemic vascular resistance index induced by the L-NAME injection. This result suggests that a NOS blockade may be a possible supportive option for oxygenation by iNO treatment in neonatal Gram-negative bacterial pneumonia and sepsis.

Pretreatment with N-nitro-L-arginine Methyl Ester Improved Oxygenation After Inhalation of Nitric Oxide in Newborn Piglets with Escherichia coli Pneumonia and Sepsis

We evaluated the effects of a combined therapy of pre-blockade endogenous nitric oxide synthase (NOS) with N-nitro-L-arginine methyl ester (L-NAME) and continuous inhaled NO (iNO) on the gas exchange and hemodynamics of Escherichia coli pneumonia and sepsis in newborn piglets. Seven to ten day old ventilated newborn piglets were randomized into 5 groups: control, E. coli pneumonia control, pneumonia with iNO 10 ppm, pneumonia pre-treated with L-NAME 10 mg/kg, and pneumonia with the combined therapy of L-NAME pretreatment and iNO. E. coli pneumonia was induced via intratracheal instillation of Escherichia coli, which resulted in progressively decreased cardiac index and oxygen tension; increased pulmonary vascular resistance index (PVRI), intrapulmonary shunting, and developed septicemia at the end of 6 hr experiment. iNO ameliorated the progressive hypoxemia and intrapulmonary shunting without affecting the PVRI. Only two of 8 animals with L-NAMEpretreated pneumonia survived. Whereas when iNO was added to infected animals with L-NAME pretreatment, the progressive hypoxemia was abolished as a result of a decrease in intrapulmonary shunting without reverse of the high PVRI and systemic vascular resistance index induced by the L-NAME injection. This result suggests that a NOS blockade may be a possible supportive option for oxygenation by iNO treatment in neonatal Gram-negative bacterial pneumonia and sepsis.

Participación del óxido nítrico y los metabolitos del ácido araquidónico vía citocromo P450 en la regulación de la presión arterial / Participation of nitric oxide and arachidonic acid metabolites via cytochrome-p450 in the regulation of arterial blood pressure

El óxido nítrico y los metabolitos del ácido araquidónico vía citocromo P450 contribuyen a la regulación de la presión arterial. La modificación en la síntesis de estos autacoides conduce a hipertensión arterial, sin embargo, se desconoce si existe interacción. Por ello, decidimos estudiar el papel modulador del óxido nítrico y los metabolitos del ácido araquidónico vía citocromo P450, y su interacción, sobre la presión arterial y el contenido renal de citocromo P450. Ratas Wistar macho fueron divididas por grupos: 1) Control, 2) L-NAME (100mg/kg/d v.o.), 3) L-NAME + SnCl2 (10mg/kg/d i.p.) y 4) L-NAME + dexametasona (1mg/kg/d s.c.). Se determinó la presión arterial sistólica y la concentración de nitritos por HPLC en orina y sangre. Los valores de presión arterial sistólica fueron: control 97 ± 7 mmHg, L-NAME 151 ± 4.6 mmHg, L-NAME + SnCl2 133 ± 3 mmHg, y L-NAME + dexametasona 152 ± 4.5 mmHg. Los nitritos en orina fueron: 1) 1.832 ± 0.32, 2) 1.031 ± 0.23, 3) 1.616 ± 0.33 y 4) 1.244 ± 0.33 μmol/mL y en sangre: 1) 0.293 ± 0.06, 2) 0.150 ± 0.05, 3) 0.373 ± 0.13 y 4) 0.373 ± 0.07 μmol/mL. El contenido renal de citocromo P450 fue abatido con el tratamiento de L-NAME + SnCl2, y una respuesta semejante se observó con L-NAME + dexametasona. Tanto óxido nítrico como los metabolitos del ácido araquidónico vía CYP participan en la regulación de la presión arterial. Además, el óxido nítrico contribuye regulando parcialmente el contenido renal del citocromo P450.

Nitric oxide and cytochrome P450 arachidonic acid metabolites participate in blood pressure regulation. The synthesis of these autacoids leads to arterial hypertension. However, it is not known whether there is an interaction between them. Therefore, we studied the modulatory effect of nitric oxide and cytochrome P450-arachidonic acid metabolites, their interaction on blood pressure, and the renal content of cytochrome P450. Male Wistar rats were divided: 1) control, 2) L-NAME (100 mg/kg/d p.o.), 3) L-NAME + SnCl2 (10 mg/kg/d i.p.), and 4) L-NAME + dexamethasone (1 mg/kg/d s.c.). We measured blood pressure and collected urine and blood for nitric oxide measurement. NO2 was quantified by HPLC. Blood pressure was: control, 97 ± 7 mmHg; L-NAME, 151 ± 4.6 mmHg; L-NAME + SnCl2, 133 ± 3 mmHg, and L-NAME + dexamethasone 152 ± 4.5 mmHg. Urine nitrite concentration was: 1) 1.832 ± 0.32, 2) 1.031 ± 0.23, 3) 1.616 ± 0.33, and 4) 1.244 ± 0.33 μmol/mL, while the concentration in blood was: 1) 0.293 ± 0.06, 2) 0.150 ± 0.05, 3) 0.373 ± 0.13, and 4) 0.373 ± 0.07 μmol/ mL. L-NAME + SnCl2 decreased cytochrome P450 renal content, and L-NAME + dexamethasone showed a similar response. In conclusion, both, nitric oxide and CYP-arachidonic acid metabolites play a role in the regulation of blood pressure. Nitric oxide also partially regulates renal cytochrome P450 content. (Arch Cardiol Mex 2003; 73:98-104).

Estudo quantitativo da microcirculaçäo miocárdica na hipertensäo arterial por progressiva inibiçäo da síntese do óxido nítrico / Quantitative study of myocradial microcirculation in arterial hypertension due to progressive inhibition of NO synthesis

OBJECTIVE- To study the quantitative changes in intramyocardial blood vessels in rats in whom nitric oxide synthesis was inhibited. METHODS - Four groups of 10 rats were studied: control (C25 and C40) and L-NAME(L25 and L40). The animals L25 and L40 received L-NAME in the dosage of 50mg/kg/day for 25 and 40 days, respectively. On days 26 and 41 the animals in groups 25 and 40 were sacrificed. Analysis of the myocardium was performed using light microscopy and stereology. RESULTS - Arterial blood pressure and heart weight increased 74.5 and 57.8 per cent after 25 days and 90.2 and 34.6 per cent after 40 days, respectively. Comparing the L-NAME rats with the respective controls revealed that vessel volume density decreased 31.3 per cent after 40 days, and the vessel length-density decreased 53.5 per cent after 25 days and 25.7 per cent after 40 days. The mean cross-sectional area of the vessels showed an important reduction of 154.6 per cent after 25 days. The intramyocardial vessels decreased significantly in length- density in the L-NAME animals. The mean cross-sectional area of the vessels, which normally increases during heart growth between 25 and 40 days, showed a precocious increase by the 25th day in the L-NAME rats. This suggests an increase of the size of the heart, including blood vessels. CONCLUSION - The inhibition of the NO synthesis provokes rarefaction in the intramyocardial vessels that progresses with the time of administration of L-NAME.

Reparaçäo miocárdica quando em uso de baixa dosagem e longa duraçäo de inibidor da síntese do óxido nítrico: miofibroblastos, colágeno tipo III e fibronectina / Myocardial repair with long-term and low-dose administration of a nitric oxide synthesis inhibitor: myofibroblasts, type III collagen and fibronectin

Objetivo - Estudar o processo de reparação miocárdica em ratos hipertensos sob inibição da síntese do óxido nítrico. Métodos - Foram estudados dois grupos de animais (controle e L-NAME 12 mg/kg/dia). A presença de colágeno tipo III, fibronectina e células contendo a-cima de músculo liso foi examinada por técnica imuno-histoquímica. Resultados - A fibronectina foi observada em ambas as lesões, recentes e tardias, enquanto que o colágeno tipo III foi observado, principalmente, nas áreas de cicatrização incompleta entre os miócitos e em torno dos ramos das artérias coronárias. As áreas de lesões recentes e tardias mostraram a presença de células fusiformes. A análise imuno-histoquímica demonstrou positividade para a actina de músculo liso nestes células. Conclusão - As células que expressam alpha-actina de músculo liso no miocárdio de ratos hipertensos estão associadas a acúmulo de colágeno tipo III e de fibronectina nas áreas de lesão.

Efectos cardiovasculares del óxido nítrico a nivel espinal en ratas anestesiadas / Cardiovascular effects of spinal nitric oxide in anesthetized rats

En ratas anestesiadas con pentobarbital, la inyección intratecal del precursor de la síntesis de óxido nítrico, la L-arginina (10 y 20 µmoles), produjo una disminución en la presión arterial media, mientras que el inhibidor de la síntesis de óxido nítrico, el NG-nitro-L-arginina metil éster (L-NAME: 0,1-10 µmoles) produjo un efecto presor dosis-dependiente. La respuesta presora al L-NAME fue prevenida por el pretratamiento con L-arginina. Los isómeros inactivos (D-NAME y D-arginina) no modificaron la presión arterial media. El dador de óxido nítrico, nitroprusiato de sodio (0,125-0,250 µmoles) indujo una respuesta hipotensora seguida por un efecto presor. La respuesta dual al nitroprusiato de sodio, como así también el efecto hipotensor de L-arginina fueron abolidos por un inhibidor de la guanilato ciclasa, el azul de metileno (0,30 µmoles, inyección intratecal). El bloqueo de la transmisión nicotínica ganglionar con hexametonio (10 mg/kg, i.v.) redujo los efectos hipotensores de L-arginina y nitroprusiato de sodio y previno casi totalmente los efectos presores de L-NAME y nitroprusiato de sodio. El efecto presor del L-NAME fue abolido por el antagonista de receptores de glutamato de tipo NMDA, el ácido 2-amino-5-fosfonovalérico (AVP: 30 nmoles, inyección intratecal). Estos resultados sugieren que en la médula espinal de ratas anestesiadas con pentobarbital, el óxido nítrico produce efectos tanto inhibitorios como excitatorios sobre la actividad preganglionar simpática relacionada con el control de la presión arterial. La síntesis de óxido nítrico estaría tónicamente activada a través de la estimulación de receptores a glutamato de tipo NMDA