Increase In Nitric Oxide Metabolites Research Articles

Assessment of the accuracy of testicular dysfunction detection in male donkey (Equus asinus) with the aid of colour‐spectral Doppler in relation to plasma testosterone and serum nitric oxide levels

This study aimed to determine the usefulness of colour and pulsed Doppler modes for the accurate diagnosis of donkeys suffering from subfertility to determine whether testicular vascularity assessment could be an indicator for sperm functionality. The study sample was composed of 10 male donkeys with normospermia (control group) and 10 donkeys with hypospermia. Animals underwent scrotal circumference measurement, testicular Doppler examination, seminal evaluation, blood sampling and hormonal assay. Semen volume and concentration were significantly (p≤.05) lower in the subfertile group (30.25±1.22ml and 89.44±2.55×106 /ml) as compared with the control group (82.76±1.65ml and 452.78±1.25×106 /ml), and total sperm/ejaculation was significantly (p≤.05) higher in the normal donkeys (28.30±2.32×109 /total ejaculated) as compared with the subfertile group. Intratesticular coloured area showed a marked decline in the hypospermic males. There was no significant difference between the two groups in testosterone level, although the normal group showed an increase in nitric oxide metabolites. Both Doppler indices of the three branches of the testicular artery were elevated significantly (p≤.05) in abnormal donkeys, whereas Doppler peak systolic and end-diastolic velocities were increased in the normal group. Male donkeys with subfertility demonstrated lower arterial vascularity parameters in the form of intratesticular coloured area and blood flow rate; therefore, the most optimal parameters for differentiating subfertile hypospermic from normospermic donkeys were found to be the two Doppler indices, velocities parameters, testicular blood flow rate and nitric oxide levels.

Mineralocorticoid receptor blockade improves arginine transport and nitric oxide generation through modulation of cationic amino acid transporter-1 in endothelial cells

Blockade of the mineralocorticoid receptor (MCR) has been shown to improve endothelial function far beyond blood pressure control. In the current studies we have looked at the effect of MCR antagonists on cationic amino acid transporter-1 (CAT-1), a major modulator of endothelial nitric oxide (NO) generation. Using radio-labeled arginine, {[3H] l-arginine} uptake was determined in human umbilical vein endothelial cells (HUVEC) following incubation with either spironolactone or eplerenone with or without silencing of MCR. Western blotting for CAT-1, PKCα and their phosphorylated forms were performed. NO generation was measured by using Griess reaction assay. Both Spironolactone and eplerenone significantly increased endothelial arginine transport, an effect which was further augmented by co-incubation with aldosterone, and blunted by either silencing of MCR or co-administration of amiloride. Following MCR blockade, we identified two bands for CAT-1. The addition of tunicamycin (an inhibitor of protein glycosylation) or MCR silencing resulted in disappearance of the extra band and prevented the increase in arginine transport. Only spironolactone decreased CAT-1 phosphorylation through inhibition of PKCα (CAT-1 inhibitor). Subsequently, incubation with either MCR antagonists significantly augmented NO2/NO3 levels (stable NO metabolites) and this was attenuated by silencing of MCR or tunicamycin. GO 6076 (PKCα inhibitor) intensified the increase of NO metabolites only in eplerenone treated cells. In conclusion spironolactone and eplerenone augment arginine transport and NO generation through modulation of CAT-1 in endothelial cells. Both MCR antagonists activate CAT-1 by inducing its glycosylation while only spironolactone inhibits PKCα.

LEVELS OF NITRIC OXIDE METABOLITES IN RATS WITH HEPATOPULMONARY SYNDROME

<p>Background. System of nitric oxide (NO), which consists of NO, and its metabolites, is very important for<br />various biological processes. NO is signalling molecules and mediators of intracellular and intercellular interaction<br />that causes relaxation of smooth muscles of blood vessel walls, inhibits platelet aggregation and their adherence,<br />is involved in the transmission of nerve impulses, cell proliferation.<br />Objective. The aim of our research was to study the content of nitric oxide metabolites in blood serum and<br />bronchoalveolar lavage, to substantiate their role in pathogenesis of hepatopulmonary syndrome in<br />experiment.<br />Methods. The experiments were performed on 56 outbread male rats, 180-220 g in weight. The first experimental<br />model of hepatopulmonary syndrome (HPS) was made by imposition of double ligature on common<br />bile duct and its further dissection with a scalpel. The second experimental HPS model was made by 8-week intragastric<br />administration of oil solution CCl4 (400 g per 1 L), 0.5 ml per 100 g of body weight on the first day of<br />the experiment, 0.3 ml per 100 g on the third day of the experiment and then every third day until the end of the<br />experiment 0.3 ml per 100 g. A mixture of corn flour, lard and cholesterol and alcohol solution was added to the<br />standard diet of the rats.<br />Results. The total content of nitric oxide metabolites in blood serum of the rats of the experimental group<br />No.1 (on the 31st day after the common bile duct ligation) was significantly increased in 3.9 times (p1<0,001) if<br />compared with the control group №1. In the rats of the 2nd experimental group (with carbon tetrachloride induced<br />cirrhosis) the total content of nitric oxide metabolites in blood serum also significantly increased in 3.1 times<br />(p1<0,001). Comparison of nitric oxide metabolites content in blood serum and bronchoalveolar lavage, which<br />directly indicated about the processes in lung tissue, was great importance.<br />Conclusions. So, in rats with experimental hepatopulmonary syndrome activation of nitroxydergic process<br />by significant increase in nitric oxide metabolites in blood serum and bronchoalveolar lavage took place.<br />KEYWORDS: hepatopulmonary syndrome, nitric oxide metabolites.</p>

POSSIBLE WAYS OF STIMULATION OF NITRIC OXIDE PRODUCTION AS THE MAIN INDUCTOR OF ENDOTHELIAL DYSFUNCTION USING CARDIOTROPIC DRUGS IN PATIENTS WITH PERIPHERAL OCCLUSIVE ARTERIAL DISEASE

The open randomized trial meeting the ICH GCP criteria included 4 groups of patients with peripheral occlusive arterial disease, stage IIA-III according to the Fontaine classification in modification by Pokrovsky. The first group was given 5mg of nebivolol qd po, the second was given perindopril 5, 10 mg qd po, the third - L-arginine 500mg bid po during 30 days. Group 4 was a control group. After a 30-days period of conservative therapy we observed a 70% increase of NO level in the first group, 95% increase in the 2nd group and 539% increase in the 3rd. A reliable increase of nitric oxide metabolites correlated with improvement in clinical findings as well as functional tests. Treadmill test improved by 22%, 20%, and 32% respectively. Rheographic test improved in all study groups and its values exceeded the normal ones by 15-25% (P

Nitric-Oxide Synthase Mediates the Ability of Darbepoetin Alfa to Attenuate Pre-Existing Spatial Working Memory Deficits in Rats Subjected to Transient Global Ischemia

Erythropoietin has been reported to improve the behavioral performance of healthy mice in tests thought to depend on synaptic plasticity in the CA1 region of the hippocampus. We show here for the first time that a single injection of the erythropoietin analog darbepoetin alfa reverses pre-existing cognitive deficits in adult rats that had been subjected to transient global ischemia produced by four-vessel occlusion (4-VO). Quantification of neuronal density demonstrated that 12 min of 4-VO selectively killed more than 90% of CA1 neurons in the dorsal hippocampus. Rats that had sustained a bilateral loss of hippocampal CA1 neurons in this range (4-VO rats) displayed more errors and longer escape latencies in the Barnes maze compared with sham-operated controls. A single injection of darbepoetin alfa (5000 U/kg i.p.) 4 h before behavioral testing decreased deficits in escape latency for 4-VO rats but not sham-operated controls. This improvement in spatial working memory performance was correlated with increased levels of nitric-oxide metabolites in the ventral hippocampus. Systemic administration of the nitric-oxide synthase inhibitor N(G)-nitro-L-nitro-arginine methyl ester reversed the increase in nitric-oxide metabolites and improvements in spatial working memory produced by darbepoetin alfa (5000 U/kg, i.p.) at a dose (10 mg/kg, i.p.) that did not impair the spatial working memory performance of intact rats. Taken together, these findings suggest that darbepoetin alfa reverses pre-existing spatial working memory deficits resulting from transient global ischemia by increasing the activity of nitric-oxide synthase, an enzyme implicated in synaptic plasticity.

Pre-emptive anti-hyperalgesic effect of electroacupuncture in carrageenan-induced inflammation: Role of nitric oxide

Central sensitization theory has been defined as pivotal for understanding the excitability changes in central neurons following peripheral inflammation or neuropathic injury. Considerable evidence has demonstrated that activation of the N-methyl- d-aspartate (NMDA) subtype of glutamate receptors and subsequent nitric oxide (NO) production are the key in these changes. Consequently, neuromodulator drugs have been developed during the last decades. The electroacupuncture (EA) that acts as biochemical modulator in the spinal horn cord would prevent these changes. The aim of this study was to determine the thermal anti-hyperalgesic effect of EA (10 Hz, 3 mA) and its combination with l-NAME as nitric oxide synthase (NOS) inhibitor in carrageenan-induced hyperalgesia in rats. Also, it investigated the changes in the plasmatic concentrations of NO metabolites. Moreover, the EA combination with sub-effective dose of ketamine as a NMDA antagonist was tested. The EA pre-treatment conducted in unsedated, unrestrained and conscious animals showed a thermal anti-hyperalgesic effect in correspondence with plasmatic increase of NO metabolites. The l-NAME (30 mg/kg) pre-administration decreased significantly the plasmatic concentrations of NO 2 −/NO 3 − and suppressed the anti-hyperalgesic effect of EA. The combination of EA with ketamine enhanced the anti-hyperalgesic effect. These data constitute the first report that suggested the participation, at least in part, of the l-arginine–NOS–NO–GMPc pathway activation in anti-hyperalgesic effect of EA in carrageenan-induced inflammation model.

Training-induced increase in nitric oxide metabolites in chronic heart failure and coronary artery disease: an extra benefit of water-based exercises?

Rehabilitation programs involving immersed exercises are more and more frequently used, with severe cardiac patients as well. This study investigated whether a rehabilitation program including water-based exercises has additional effects on the cardiovascular system compared with a traditional land-based training in heart disease patients. Twenty-four male stable chronic heart failure patients and 24 male coronary artery disease patients with preserved left ventricular function participated in the study. Patients took part in the rehabilitation program performing cycle endurance exercises on land. They also performed gymnastic exercises either on land (first half of the participants) or in water (second half). Resting plasma concentration of nitric oxide metabolites (nitrate and nitrite) and catecholamine were evaluated, and a symptom-limited exercise test on a cycle ergometer was performed before and after the rehabilitation program. In the groups performing water-based exercises, the plasma concentration of nitrates was significantly increased (P = 0.035 for chronic heart failure and P = 0.042 for coronary artery disease), whereas it did not significantly change in the groups performing gymnastic exercise on land. No changes in plasma catecholamine concentration occurred. In every group, the cardiorespiratory capacity of patients was significantly increased after rehabilitation. The water-based exercises seemed to effectively increase the basal level of plasma nitrates. Such changes may be related to an enhancement of endothelial function and may be of importance for the health of the patients.

Effect of Telmisartan on Nitric Oxide–Asymmetrical Dimethylarginine System

Telmisartan, in addition to blocking angiotensin (Ang) II type 1 receptor (AT(1)R), activates peroxisome proliferator activated receptor gamma (PPARgamma) signaling that interferes with nitric oxide (NO) system. Because aging of endothelial cells (ECs) is hallmarked by a reduction in NO synthesis, we hypothesized that telmisartan increases NO formation by regulated asymmetrical dimethylarginine (ADMA)-dimethylarginine dimethylaminohydrolase (DDAH)-system through blocking AT(1)R and activating PPARgamma signaling. To test this hypothesis, ECs were cultured with telmisartan, eprosartan, Ang II, and GW9662 (PPARgamma antagonist) until the twelfth passage. During the process of aging, PPARgamma protein expression decreased significantly, whereas the expression of AT(1)R increased. Telmisartan reversed these effects and dose-dependently decreased reactive oxygen species and 8-iso-prostaglandin (PG) F(2alpha) formation. This effect was associated with an upregulated activity and protein expression of DDAH, accompanied by a decrease in ADMA concentration, an increase in NO metabolites, and delayed senescence. Blockade of PPARgamma signaling by GW9662 or PPARgamma small-interference RNA prevented the effect of telmisartan on ADMA-DDAH-NO system. Coincubation with Ang II did not affect the effect of telmisartan-delayed senescence, whereas Ang II itself accelerated endothelial aging. Moreover, AT(1)R blocker eprosartan that did not influence PPARgamma protein expression had no effect on ADMA system and senescence. We have demonstrated that telmisartan mainly by activating PPARgamma signaling can alter the catabolism and release of ADMA as an important cardiovascular risk factor. We therefore propose that telmisartan translationally and posttranslationally upregulated DDAH expression via activation of PPARgamma signaling, causing ADMA to diminish and increase NO synthesis sufficient to delay senescence.

Early upregulation of iNOS mRNA expression and increase in NO metabolites in pressurized renal epithelial cells

Pressure is an important physiological regulator, but under abnormal conditions it may be a critical factor in the onset and progression of disease in many organs. In vivo, proximal tubular epithelial cells are subjected to pressure as a result of ureteral obstruction, which may influence the production of nitric oxide (NO), a ubiquitous multifunctional cytokine. To directly explore the effect of pressure on the expression and activity of NO synthase (NOS) in cultured proximal tubular epithelial cells, a novel pressure apparatus was developed. Cells were subjected to pressures of 20-120 mmHg over time (5 min-72 h). RT-PCR demonstrated an increase in inducible NOS (iNOS) and sGC, while endothelial NOS remained unchanged. Real-time PCR (qPCR) confirmed an earlier induction of iNOS transcript subjected to 60 mmHg compared with cytokine mix. iNOS protein expression was significantly increased following 60 mmHg of pressure for 24 h. Use of nuclear factor-kappaB inhibitors was shown to prevent the increase in iNOS expression following 60 mmHg for 2 h. NO and cGMP were increased with the application of pressure. The addition of the irreversible iNOS inhibitor (1400W) was shown to prevent this increase. We demonstrate that with the use of a simply designed apparatus, pressure led to an extremely early induction of iNOS and a rapid activation of NOS activity to increase NO and cGMP in proximal tubule epithelial cells. The rapid effects of pressure on iNOS may have important implications in the obstructed kidney.

Increased Nitrosative and Oxidative Stress in Platelets of Migraine Patients

The molecular mechanisms of migraine have not been fully clarified yet. Increased nitrosative and oxidative stress may be associated with migraine attacks. Platelets may play an important role in migraine patients and they can reflect the lability of tissues to nitrosative/oxidative stress. In the present study, we aimed to determine the levels of nitrosative and oxidative stress markers in platelets of migraine patients during headache-free and attack periods. A total of 56 subjects (22 migraine without aura, 14 migraine with aura, and 20 age- and sex-matched healthy controls) were included in the study and nitric oxide (NO) metabolites, malondialdehyde (MDA), and thiol (SH) groups were measured in platelets. During migraine attacks, platelet levels of nitrate, nitrite and MDA were significantly higher in migraineurs than these in control subjects (p = 0.042, p = 0.005 and p = 0.042, respectively). By contrast, during headache-free period, no statistically significant differences were found in the platelet levels of nitrate, nitrite and MDA between migraineurs and controls (p > 0.05), although the marginal increases were detected in migraineurs. These results suggest that increased biomarkers of nitrosative and oxidative stress in platelets may be important in migraine patients, especially during attacks; increase of NO metabolites in platelets during attacks supports the opinion that NO may play a modulatory role in biological processes particularly by vasodilatation in migraine attacks. Therefore, MDA and NO metabolites may serve as useful markers to show the increased vulnerability to nitrosative and oxidative stress in migraine patients.

Phenolic Content of Virgin Olive Oil Improves Ischemic Reactive Hyperemia in Hypercholesterolemic Patients

The goal of this study was to evaluate the effects of the phenolic content of virgin olive oil on endothelial reactivity. Endothelial-dependent vasodilatation is impaired during the postprandial state, and oxidative stress could play a key role in its development. Twenty-one hypercholesterolemic volunteers received two breakfasts, using a randomized sequential crossover design. Both arms received the same olive oil, but one had its phenolic acid content reduced from 400 to 80 ppm. Ischemic reactive hyperemia (IRH) was measured with a laser-Doppler procedure at baseline and 2 h and 4 h after oil intake. Postprandial plasma concentrations of lipid fractions, lipoperoxides (LPO), 8-epi prostaglandin-F(2alpha), and nitrates/nitrites (NO(x)) were obtained at baseline and after 2 h of the fat meal. The intake of the polyphenol-rich breakfast was associated with an improvement in endothelial function, as well as a greater increase in concentrations of NO(x) (p < 0.001) and a lower increase in LPO (p < 0.005) and 8-epi prostaglandin-F2alpha (p < 0.001) than the ones induced by the low polyphenol fat meal. A positive correlation was found to exist between NO(x) and enhanced endothelial function at the second hour (r = 0.669; p < 0.01). Furthermore, a negative correlation was found between IRH and LPO (r = -0.203; p < 0.05) and 8-epi prostaglandin-F2alpha levels (r = -0.440; p < 0.05). A meal containing high-phenolic virgin olive oil improves ischemic reactive hyperemia during the postprandial state. This phenomenon might be mediated via reduction in oxidative stress and the increase of nitric oxide metabolites.

Influence of vaccination on the nitric oxide response of gilthead seabream following infection with Photobacterium damselae subsp. piscicida

The nitric oxide (NO) response of vaccinated and non-vaccinated juvenile gilthead seabream was studied in vivo and the NO response of isolated kidney macrophages of fish was studied in vitro. Fish were vaccinated with formalin-killed Photobacterium damselae subsp. piscicida ( Pdp) with or without Freund's incomplete adjuvant (FIA) and control fish received phosphate buffered saline (PBS). Thirty days later, fish were injected with a sublethal dose of Pdp and 3 fish/group were bled at time periods thereafter and serum nitrite and citrulline levels were determined as a measure of the NO response. All infected groups showed an increase in NO metabolites from 6 h to 27 days, with peak levels at 24 h. However, the response in bacterin-vaccinated fish was significantly higher than in the non-vaccinated group and the bacterin plus FIA resulted in a further significant enhancement. Similarly enhanced NO responses were produced in vitro by isolated macrophages obtained from vaccinated compared with non-vaccinated fish 30 days after vaccination following infection, with the response in macrophages from fish vaccinated with the bacterin plus FIA being significantly higher than those from fish vaccinated with the bacterin alone. Thus, vaccination resulted in an enhanced NO response to infection with Pdp in vivo and in vitro. Furthermore, the level of protection of fish to experimental challenge with virulent Pdp correlated with the level of the NO responses in the different groups.

Involvement of L-arginine-nitric oxide system in the response of isolated trachea to reactive oxygen species.

The aim of this study was to investigate the effect of reactive oxygen species (ROS), generated by electrolysis of Krebs-Henseleit solution (GE-KHS), on isolated guinea pig trachea and to assess the possible involvement of nitric oxide (NO) in the observed effects. The isolated trachea was superfused in GE-KHS, generating H2O2 and hypochlorous acid (HOCl), both of which slowly increased in the organ bath and reached final stable concentrations of 42 and 63 microM, respectively, at the rate of 20 ml/min(-1), and 261 and 245 microM, respectively, at the rate of 5 ml/min(-1). ROS GE-KHS-induced relaxation of tracheal rings was preceded by a small transient contraction in 40% and 65% of experiments when tracheal rings were superfused at the rate of 20 ml/min(-1) and 5 ml/min(-1), respectively. Removal of tracheal epithelium abolished the relaxation of the trachea induced by ROS GE-KHS and unmasked or potentiated trachealis contraction. The ROS GE-KHS-induced changes in trachealis tension were accompanied by an increase in thiobarbituric acid reactive substances (TBARS) and a decrease in nonprotein (NP) thiols in the trachea. These changes were inhibited by treatment with the antioxidant N-acetylcysteine (100 microM). Pretreatment of tracheal rings with the inhibitor of NO synthase (NOS) N(omega)-nitro-L-arginine (L-NOARG; 100 microM) for 20 min prior to exposure to ROS GE-KHS decreased the ROS GE-KHS-induced relaxation. When L-NOARG (100 microM) was present in the superfusing solution, not only 20 min before but also during superfusion with ROS GE-KHS, the evoked trachealis relaxation was reduced in the first 15 min but was enhanced in the 30th min. This late enhancement of relaxation was accompanied by a 12-fold increase in nitric oxide metabolites (NO(x)). ROS GE-KHS-induced elevation of TBARS levels in the trachea was decreased to 63% by pretreatment with L-NOARG (100 microM). Elevation of TBARS levels induced by incubation of brain liposomes with a hydroxyl radical generating system was decreased to 90% by L-NOARG (10, 100 microM), while the antioxidant stobadine (100 microM) nearly completely inhibited the evoked lipid peroxidation. In comparison with Trolox, L-NOARG exerted a slight scavenging effect on the 1,1-diphenyl-2-picrylhydrazyl radical. The presence of L-arginine and D-arginine in the superfusion fluid for 15-20 min before and during exposure of the trachea to ROS GE-KHS inhibited trachealis relaxation. Results indicate that epithelium derived NO may participate in the response of guinea pig trachea to ROS GE-KHS. The presence of L-NOARG in the bathing fluid during superfusion with ROS GE-KHS gave rise to NO(x), with relaxing activity. L- and D-arginine induced an inhibition of the relaxatory response to ROS GE-KHS and partially prevented a ROS-induced decrease in NP thiols. The involvement of the small antioxidant effects of L-NOARG and L- and D-arginine in the above mentioned actions of L-NOARG and L-arginine requires additional investigation.

N-tosyl- l-phenylalanyl-chloromethylketone reduces hypoxic–ischemic brain injury in rat pups

N-tosyl- l-phenylalanyl-chloromethylketone (TPCK) in vitro blocks apoptotic pathways leading to cell death. We wished to see if TPCK would reduce brain injury in vivo. Seven-day-old rat pups had the right carotid artery ligated and then received either vehicle or TPCK (5 to100 mg/kg i.p.). They were then given 8% oxygen for 2.25 h. Twenty-two days later, the cerebral hemispheres were weighed to determine the reduction in size in the right hemisphere. TPCK decreased the reduction in right hemisphere weight from 15±3% (vehicle, n=20), to 4±2% (10 mg/kg, n=19, P<0.01). TPCK reduced the number of cells staining for DNA breaks 3 days after injury from 1729±275 mm −2 (vehicle, n=8) to 550±236 mm −2 (10 mg/kg TPCK, n=9, P<0.01), decreased the amount of DNA fragmentation 3 days after injury by gel electrophoreses (20 mg/kg, n=16, P<0.01) and eliminated the increase in nitric oxide metabolites 6 h after injury (vehicle 1.5±0.4, n=10; and 20 mg/kg TPCK 0.0±0.1 nM/mg protein, n=10, P<0.001). TPCK pretreatment in the newborn rat model of hypoxic–ischemic brain injury reduces DNA fragmentation, nitric oxide production and brain injury.

Protective effect of aminoguanidine on hypoxic-ischemic brain damage and temporal profile of brain nitric oxide in neonatal rat.

Nitric oxide (NO) produced by inducible NO synthase contributes to ischemic brain damage. However, the role of inducible NO synthase-derived NO on neonatal hypoxic-ischemic encephalopathy has not been clarified. We demonstrate here that aminoguanidine, a relatively selective inhibitor of inducible NO synthase, ameliorated neonatal hypoxic-ischemic brain damage and that temporal profiles of NO correlated with the neuroprotective effect of aminoguanidine. Seven-day-old Wister rat pups were subjected to left carotid artery occlusion followed by 2.5 h of hypoxic exposure (8% oxygen). Infarct volumes (cortical and striatal) were assessed 72 h after the onset of hypoxia-ischemia by planimetric analysis of coronal brain slices stained with hematoxylin-eosin. Aminoguanidine (300 mg/kg i.p.), administered once before the onset of hypoxia-ischemia and then three times daily, significantly ameliorated infarct volume (89% reduction in the cerebral cortex and 90% in the striatum; p<0.001). NO metabolites were measured by means of chemiluminescence using an NO analyzer. In controls, there was a significant biphasic increase in NO metabolites in the ligated side at 1 h (during hypoxia) and at 72 h after the onset of hypoxia (p<0.05). Aminoguanidine did not suppress the first peak but significantly reduced the second one (p<0.05), and markedly reduced infarct size in a neonatal ischemic rat model. Suppression of NO production after reperfusion is a likely mechanism of this neuroprotection.

Intra-coronary administration of L-arginine aggravates myocardial stunning through production of peroxynitrite in dogs.

The aim of this study was to investigate how the enhanced nitric oxide (NO) production by intra-coronary infusion of L-arginine acts in myocardial stunning in dogs by focusing on the involvement of peroxynitrite, a reaction product of NO and superoxide anion. Dogs were divided into six groups; a control non-treated group (CON, n = 9), and NG-nitro L-arginine methyl ester (L-NAME, n = 6), 1 mM L-arginine (L-ARG, n = 8), D-arginine (D-ARG, n = 6), L-arginine plus superoxide dismutase (L-ARG + SOD, n = 6), and SOD alone (SOD, n = 6) treated groups. L-NAME, or L- or D-arginine was continuously infused into the left anterior descending coronary artery (LAD) starting just prior to reperfusion, whereas SOD was intravenously injected before occlusion. During 120 min of reperfusion after 15 min occlusion of LAD, myocardial contractile function in the ischemic region gradually recovered and reached approximately 70% of the preischemic level in CON, D-ARG and SOD, but it remained dyskinetic (-46%) in L-ARG. On the other hand, it was improved in L-NAME (90%). Tissue malondialdehyde was elevated (p < 0.005) after reperfusion, and myocardial NO metabolites measured by an intratissue-microdialyzer increased (approximately 150%, p < 0.05) in the ischemic region during reperfusion in L-ARG but not in the CON, L-NAME, D-ARG or SOD groups. In the L-ARG + SOD group, L-arginine-induced contractile dysfunction and elevation of malondialdehyde were prevented, but the increase in NO metabolites remained. These results suggest that L-arginine aggravated myocardial stunning through oxidative stress and the cytotoxicity was caused by NO derivatives but not by NO itself. The formation of nitrotyrosine, a footprint of peroxynitrite, was immunohistochemically confirmed in the ischemic region of L-ARG. Our results demonstrate for the first time in vivo that NO has a detrimental role in myocardial stunning through the production of peroxynitrite.

Acute effects of transdermal estradiol administration on plasma levels of nitric oxide in postmenopausal women

To investigate the acute effects of transdermal E2 administration on nitric oxide (NO) plasma levels in postmenopausal women. Randomized, placebo-controlled trial. Normal human volunteers in an academic research environment. Twenty healthy postmenopausal women. Transdermal administration of 100 micrograms/d E2 or placebo. Plasma concentrations of NO stable oxidation products and serum concentrations of E2 were assessed before and 24 hours after the administration. In the group treated with E2 mean concentration of NO metabolites 24 hours after patch application (37.31 +/- 7.62 mumol/L) resulted significantly higher than baseline (21.04 +/- 5.71 mumol/L) and the control group (23.50 +/- 4.03 mumol/L). The correlation between the mean percent increase in NO metabolites and absolute E2 concentrations 24 hours after the E2 administration was statistically significant. Transdermal administration of E2 to healthy postmenopausal women increases the plasma levels of NO and this supports the hypothesis that a NO-related mechanisms may contribute to the cardiovascular protective effect of estrogens in postmenopause.