Serum Nitrate Concentrations Research Articles

Rapid-onset endothelial dysfunction with adriamycin: evidence for a dysfunctional nitric oxide synthase.

Adriamycin (ADR) is a commonly used chemotherapeutic agent that is believed to exert its effects through the generation of oxygen free radicals. We hypothesized that administration of a single dose of ADR results in endothelial nitric oxide synthase (eNOS)-dependent generation of superoxide (O2*-) and acute endothelial dysfunction. A single dose of ADR (10 mg/kg i.v.) administered to rabbits resulted in rapid attenuation of agonist-dependent responses to acetylcholine and calcium ionophore (A23187). In vitro exposure of ring segments to ADR for < 30 min resulted in O2*- generation measured by electron spin resonance (ESR) with the spin trap segments 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO) that was abolished by endothelial denudation and incubation with diphenyliodonium (DPI) (10 microM) but not L-NMMA (10 microM). Brachial artery flow-mediated dilation (FMD) in patients undergoing chemotherapy with ADR was markedly attenuated after a single dose of ADR (6.5 +/- 1.0 to 2.5 +/- 1.1% (p = 0.0004, time to end of infusion 27 +/- 8 min) while endothelial-independent dilatation with nitroglycerin was unchanged (16.3 +/- 3.1 and 14.33 +/- 2.1% respectively, p = 0.36). Serum nitrite and nitrate concentrations fell from 50 +/- 6 micromol/l pre-ADR to 33 +/- 6 micromol/l post-ADR infusion (p = 0.0005) while serum concentrations of CD141 thrombomodulin and von Willebrand factor (vWF) activity remained unchanged after ADR infusion (36 +/- 13 to 52 +/- 22% ng/ml versus 3.25 +/- 0.98 to 3.01 +/- 0.91%, respectively, p = NS for pre versus post for both). Doppler indices of diastolic function (IVRT, DT and E/A ratios) were not altered in response to ADR. In conclusion, ADR administration results in rapid depletion of systemic NO* levels and attenuation of agonist-dependent responses in rabbits and flow-mediated dilation in the brachial artery of humans. ESR measurements in rabbit ring suggest an endothelial origin for radical production via flavin-containing oxido-reductases such as eNOS or NADPH cytochrome P450 reductase. These findings may have implications for cardiovascular complications noted with ADR.

Dietary nitrate generates potentially mutagenic concentrations of nitric oxide at the gastroesophageal junction

Twenty-five percent of absorbed dietary nitrate is re-secreted in saliva, and 30% of this is reduced to nitrite by buccal bacteria. When saliva is swallowed, the acidic gastric juice reduces the nitrite to nitric oxide. The aim of this study was to examine the anatomic distribution of nitric oxide generation within the lumen of the upper gastrointestinal tract under basal conditions and after ingesting nitrate equivalent to that in salad portion. Using custom-made sensors, the dissolved luminal nitric oxide concentration and pH were measured at 1-cm increments for 2 minutes throughout the length of the stomach and distal esophagus in 15 Helicobacter pylori-negative healthy volunteers with and without ingestion of 2 mmol potassium nitrate. Serum nitrate and saliva nitrite concentrations were also monitored. The nitrate ingestion increased mean (range) serum nitrate from 30 micromol/L (18-49) to 95 micromol/L (32-152), mean salivary nitrite from 36 micromol/L (19-153) to 252 micromol/L (32-600), and mean peak luminal nitric oxide concentration from 4.7 micromol/L (1.4-7.8) to 23.2 micromol/L (2.1-50) (P < 0.05 for each). After nitrate, the peak nitric oxide concentration occurred in 11 of the 15 (73%) subjects within 1 cm distal to the gastroesophageal pH step-up point. The mean nitric oxide concentration over the 1-cm segment immediately distal to the gastroesophageal pH step-up after nitrate was 7.5 micromol/L (range, 0.5-30.7) and was significantly higher than at all other sites. Nitric oxide concentrations greater than 50 micromol/L were observed at the precise location where neutral esophageal pH fell to acidic gastric pH. Luminal generation of nitric oxide from dietary nitrate via salivary nitrite is maximal at the gastroesophageal junction and cardia. The high concentrations of nitric oxide generated may contribute to the high incidence of mutagenesis and neoplasia at this site.

Failure of neutrophil chemotactic function in septic patients.

To investigate the in vitro chemotactic function of neutrophils obtained from patients with sepsis. Prospective study in which purified neutrophils obtained from septic patients and nonseptic control volunteers were assayed for chemotactic function induced by N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) and leukotriene B4. The sera nitrate concentrations also were quantified. University hospital. Twenty patients with sepsis caused by different infectious foci. Routine blood tests, blood or other site cultures, blood collection for neutrophil purification sera collection for nitrate assay. Neutrophils from septic patients exhibited significantly less chemotactic activity than neutrophils obtained from healthy volunteers, in response to FMLP (93.4 +/- 6.6 vs. 51 +/- 8.3 migrated neutrophils) and leukotriene B4 (90.2 +/- 10 vs. 42.4 +/- 11.6 migrated neutrophils) stimuli, in a microchemotaxis chamber assay. The impaired chemotaxis occurred mainly in neutrophils from nonsurvivor patients. The extent of neutrophil chemotaxis inhibition (survivor/nonsurvivor) was 33.43%/61.67% and 43.4%/86.98%, in response to FMLP and leukotriene B4, respectively. Increased serum nitrate (micromoles of NO2 + NO3) concentrations were detected in septic patients, compared with controls, but no differences were found between survivor (91.84 +/- 14.12) and nonsurvivor (102.6 +/- 17.36) groups. Septic patients present suppressed neutrophil chemotactic responses to FMLP and leukotriene B4 stimuli compared with healthy controls. This is accompanied by increased serum concentrations of nitrate. The impairment of neutrophil chemotaxis was observed mainly in the cells obtained from nonsurvivor patients and may thus be an additional factor contributing to disease outcome.

Helicobacter pylori infection increases serum nitrate and nitrite more prominently than serum pepsinogens.

Helicobacter pylori infection causes chronic gastritis and results in increased serum concentrations of pepsinogens I and II as well as gastrin, while the ratio of pepsinogen I to II (I : II) is decreased. Inducible nitric oxide synthase (iNOS) is induced in H. pylori-associated gastritis and may modulate inflammation. However serum nitrate and nitrite (NOx) concentrations in patients with H. pylori-induced chronic gastritis have not been reported. We examined differences in serum NOx between H. pylori-negative and positive volunteers relative to differences in pepsinogens and gastrin. Sera from 80 healthy asymptomatic volunteers younger than 36 years were analyzed for anti-H. pylori antibody, NOx, gastrin and pepsinogens. In H. pylori antibody-positive subjects serum NOx concentrations were higher than in negative subjects (p < .005). In H. pylori-negative subjects, NOx correlated with pepsinogen II (r = .405, p < .05). In subjects with low pepsinogen I or II, NOx was higher in H. pylori-positive than negative subjects (p < .001). In subjects with high pepsinogen I : II (6 or higher), serum NOx was higher in H. pylori-positive than in negative subjects. H. pylori-induced gastritis increases serum NOx concentrations more prominently than those of pepsinogen. In H. pylori-negative subjects, serum correlates with serum pepsinogen II.

Iron deficiency anemia increases nitric oxide production in healthy adolescents.

To investigate the influence of iron deficiency and iron supplementation on nitric oxide (NO) production, we measured serum iron markers, serum nitrate and nitrite (NOx) concentrations, reticulocyte maturity index (RMI), and serum transferrin receptor (sTfR) levels in 369 females aged 14-19 years. RMI was analyzed by flow cytometry, sTfR concentrations were measured by enzyme immunoassay, and serum NOx levels were tested by the Griess reaction. NOx concentrations of the subjects in iron depletion phase were significantly higher than those of healthy controls. NOx concentrations increased gradually as iron deficiency progressed and were threefold higher than for the healthy controls, when the subjects attained a frank iron deficiency anemia. In particular, the NOx concentrations were 7.5-fold higher in the patients with severe iron deficiency anemia (Hb<80 g/l) than for the subjects with high hemoglobin value (Hb>or=140 g/l). The increased NOx concentrations (132.6+/-42.1 microM) observed in the group with severe anemia decreased significantly (46.3+/-15.8 microM) after hemoglobin levels were normalized by iron supplementation ( P<0.01). NOx concentrations correlated inversely with hemoglobin levels ( r(2)=0.202, P<0.01), but correlated positively with the sTfR concentrations ( r(2)=0.322, P<0.01) and the RMI ( r(2)=0.369, P<0.01). In conclusion, iron deficiency anemia increases NO production, and elevated NOx concentrations in iron deficiency anemia return to normal with iron supplementation.

Repeated administration of protamine does not attenuate circulatory changes caused by protamine reversal of heparin in dogs

Objective: To determine whether repeated administration of protamine attenuates circulatory changes caused by protamine reversal of heparin and to evaluate the significance of nitric oxide generation. Design: Prospective, randomized, controlled, animal study. Setting: University research laboratory. Participants: Twenty-seven adult mongrel dogs. Interventions: The animals were randomly assigned to 3 groups (n = 9 in each) according to the pretreatment. The control group was pretreated with normal saline, and the 2 other groups were given 2 different doses of protamine: protamine 0.1 (protamine, 0.1 mg/kg) and protamine 1.0 (protamine, 1.0 mg/kg). Under general anesthesia, all animals were anticoagulated with intravenous heparin, 200 IU/kg. Five minutes after heparin injection, preadministered saline (control) or protamine in saline was infused during 60 seconds. Five minutes after the pretreatment, protamine, 2.0 mg/kg in control, 1.9 mg/kg in protamine 0.1, or 1.0 mg/kg in protamine 1.0, was administered intravenously during 10 seconds. Measurements and Main Results: Percent changes in mean arterial blood pressure among the 3 groups at each period were not significantly different except 60 minutes after protamine infusion. Mean pulmonary arterial pressure in the protamine 1.0 group at 5, 15, 20, and 60 minutes was higher than in the control group. Serum nitrate concentration was not significantly different among the 3 groups at baseline and 10 minutes after protamine injection. Conclusion: Repeated administration of protamine does not attenuate circulatory changes caused by protamine reversal of heparin in dogs. Nitric oxide generation does not appear to be responsible for the phenomenon. Copyright © 2001 by W.B. Saunders Company

Increased nitrite and nitrate concentrations in sera and urine of patients with cholera or shigellosis

OBJECTIVES: Nitric oxide (NO) is an important regulator of cell function. In the intestine, NO regulates blood flow, peristalsis, secretion, and is associated with inflammation and tissue injury. The objectives of this study were to assess and compare the role of NO in cholera, a noninflammatory enteric infection, and in shigellosis, a bacterial inflammation of the colon. METHODS: We determined serum and urinary concentrations of nitrite and nitrate during acute illness and early convalescence in 45 hospitalized children: 24 with cholera and 21 with shigellosis; 18 healthy children served as controls. Nitrite and nitrate concentrations were determined spectrophotometrically using Greiss reaction-dependent enzyme assay. RESULTS: Serum nitrite and nitrate concentrations were significantly ( p < 0.05) increased during acute illness compared to the early convalescence in both cholera and shigellosis. Urinary nitrite and nitrate excretions were significantly ( p < 0.01) increased during acute disease in shigellosis, but not in cholera. Nitrite concentrations correlated with stool volume (r 2 = 0.851) in cholera and with leukocytosis (r 2 = 0.923) in shigellosis. CONCLUSIONS: Both cholera and shigellosis are associated with increased production of NO, suggesting its pathophysiologic roles in these diseases.

Soluble fas levels correlate with multiple organ dysfunction severity, survival and nitrate levels, but not with cellular apoptotic markers in critically ill patients.

Apoptosis is a mode of programmed cell death (PCD). Transduction of apoptotic signals results in cellular suicide. Organ specific apoptosis has been proposed as a factor in multiple organ dysfunction syndrome (MODS). Fas is a widely occurring apoptotic signal receptor molecule expressed by almost any type of cell, which is also released in a soluble circulating form (circulating fas, sfas). In this exploratory study, we investigated the association of sfas with severity, survival, known mediators of multiple organ dysfunction, and cellular apoptotic markers on peripheral blood mononuclear cells (PBMC) in a group of 35 patients with MODS and in 35 matched controls. Critically ill patients with MODS had significantly elevated sfas levels compared to controls over time (P < .001). Increased serum concentration of circulating fas was associated with increased severity of multiple organ dysfunction. Non-survivors exhibited significantly higher sfas levels compared to survivors (P < .01) and increasing sfas was inversely associated with the likelihood of survival (P < .05). Circulating fas levels correlated highly with serum nitrate concentration, but not with fas and fasL expression on PBMC of critically ill patients. TNF-alpha and IL-6, although they appear to be mediators of both apoptosis and MODS, had no association with sfas. These results are suggestive of the need for further investigation on the role of apoptotic signaling in the development of MODS. They also suggest a potential prognostic value of sfas for SIRS/MODS clinical outcomes.

The relationship between serum nitrate and endothelin-1 concentrations in preeclampsia

Recently it was suggested that abnormal endothelial function may contribute to the pathophysiological changes observed in preeclampsia (PE). Both nitric oxide (NO) and endothelin-1 (ET-1) are vasoactive substances produced by endothelial cells. NO is a vasodilator and has been believed to be decreased in PE. ET-1 is a vasoconstrictor and has been reported to be increased in PE. We simultaneously measured NO metabolites and ET-1 in sera from women with PE and investigated the correlation of NO and ET-1 concentrations. We obtained serum samples from 11 healthy nonpregnant (NP) women, 16 normotensive pregnant (NTP) women and 17 women with PE. In this study, the serum ET-1 level was assayed by the ET-1 RIA system, and serum NO metabolites were assayed by measuring nitrite (NO 2 −) and nitrate (NO 3 −) simultaneously in an HPLC-Griess reaction system. There was a significant correlation between NOx (nitrite + nitrate) and ET-1 in sera from all 44 women (NP, NTP and PE groups) (p<0.001). Nitrite and ET-1 in sera from each group were not significantly correlated. Nitrate and ET-1 in sera from the NP and NTP groups did not significantly correlate. However, there was a significant correlation between nitrate and ET-1 in sera from the PE group (p<0.05). The serum ET-1 and nitrate concentration in the PE group was significantly higher than in the NP and NTP groups (p<0.05 and p<0.001, respectively). These findings suggest that increased production of nitrate in PE may contribute to homeostatic vasodilation against vasoconstriction caused by a higher ET-1 concentration.

Age-associated changes in nitric oxide metabolites nitrite and nitrate.

Aging is an important determinant of vascular disease. Endothelial dysfunction accompanying vascular disease may be related to cardiovascular risk factors such as aging, hypertension, and atherosclerosis. Experimental models suggest that endothelium-derived nitric oxide is reduced with aging, and this reduction is implicated in atherogenesis. The aim of this study was to determine whether increased age resulted in altered serum nitrite and nitrate levels, end-products of nitric oxide, in healthy subjects. Sixty-nine healthy individuals were divided into five different age groups: group I (6-15 years), group II (16-30 years), group III (31-45 years), group IV (46-60 years), and group V (>61 years). In these subjects, serum nitrite was measured by the Griess reaction and nitrate by the nitrate reductase method. Statistical analysis showed that serum nitrite levels were not significantly different in any of the groups, while serum nitrate concentrations exhibited significant differences (P<0.001). These findings suggest that nitric oxide synthesis and/or secretion is reduced with age and consequently endothelium-dependent vasodilation is impaired.

Serum nitrate concentrations in patients with peripheral arterial occlusive disease.

Nitric oxide (NO), an endogenous product of L-arginine oxidation, seems to account for the vasodilatatory effect of the endothelium-derived relaxing factor. It was the aim of the present study to measure serum nitrate concentrations, the degradation product of nitric oxide in patients with peripheral arterial occlusive disease (PAOD). 20 patients with PAOD in Fontaine stage IIb, 10 patients in stage III and IV respectively were included in the study. Serum samples for determination of nitrate were taken at admission after fasting overnight. Nitrate concentrations were determined using a recently developed high performance liquid chromatography which allows direct measurement of nitrate. The control group comprised 14 age and risk factor matched volunteers. We found significantly increased nitrate concentrations in patients with PAOD compared to the control group [stage IIb: 6.65 +/- 1.58 mumol/l; stage III: 6.94 +/- 1.85 mumol/l, stage IV: 7.05 +/- 1.16 mumol/l; control: 4.41 +/- 1.24 mumol/l], however no significance was calculated within the different PAOD groups. There was no association of either diabetes mellitus, hypertension and smoking behaviour with increased nitrate levels. These data might indicate that NO might be involved in adaptive vasodilatation already in the early phase of the disease. The source of nitrate in PAOD patients, however, remains unclear.

Effect of L-lysine on nitric oxide production in ovine endotoxaemia

Excess production of nitric oxide contributes to the refractory hypotension associated with sepsis and is dependent upon precursor availability, L-arginine. Endothelial uptake of L-arginine by the y+ transporter can be inhibited by another cationic amino acid, L-lysine. This study was undertaken to determine the effects of L-lysine in an anaesthetized ovine model of endotoxaemia in which nitric oxide production is known to be limited by L-arginine availability. The haemodynamic effects of i.v. L-lysine (500 mg kg-1) were compared with those of a known inhibitor of nitric oxide synthase, NG-nitro-L-arginine-methyl ester, L-NAME (25 mg kg-1) and with control animals (n = 6 per group). Serum nitrates, the stable end metabolite of nitric oxide production, were also measured. L-NAME administration caused a significant increase in systemic and pulmonary vascular resistance (P < 0.0001), mean arterial pressure (P < 0.0001) and a reduction in serum nitrate concentrations (P < 0.0001). The administration of L-lysine had no effect on systemic or pulmonary vascular resistance, mean arterial pressure or serum nitrate concentrations. We conclude that the administration of L-lysine does not inhibit nitric oxide production in this model.

Hepatic expression of inducible nitric oxide synthase transcripts in chronic hepatitis C virus infection: relation to hepatic viral load and liver injury.

Hepatitis C virus (HCV) causes acute and often also chronic liver disease. Hepatocellular injury might result from both a host response directed to inhibit viral spread and from processes initiated by the virus itself. To study mechanisms involved in hepatocellular injury, liver tissue from chronically HCV-infected patients was analyzed for the expression of the inducible isoform of nitric oxide synthase (iNOS) and for interferon gamma (IFN-gamma) by a quantitative, competitive reverse-transcription-polymerase chain reaction (RT-PCR) technique. Moreover, hepatic viral load was determined by two independent techniques, and liver tissue was evaluated histopathologically in detail. Liver tissue from HCV-infected patients was shown to express elevated levels of iNOS transcripts compared with non-HCV-infected patients. Increased iNOS transcript expression, however, was not accompanied by significantly elevated serum nitrite plus nitrate (NOx) concentration, although some of the chronic HCV-infected patients reached markedly higher serum NOx levels than the control group or healthy individuals, respectively. Hepatic iNOS expression was found to be positively correlated to hepatic HCV-RNA content on the one hand, and weakly to hepatic IFN-gamma expression, previously shown to be solely associated with hepatic necro-inflammatory activity among the histopathological parameters studied, on the other hand. In contrast to IFN-gamma transcript expression, neither hepatic iNOS expression nor hepatic HCV-RNA content were related to hepatic inflammatory activity. The presented data are compatible with the assumption that HCV might be able to stimulate iNOS expression both directly and indirectly via its capacity to induce IFN-gamma.

Long-lasting NO overproduction in cirrhotic patients with spontaneous bacterial peritonitis.

Nitric oxide production was studied in cirrhotic patients with spontaneous bacterial peritonitis (SBP) or with other infections. We followed up on the time course of serum nitrate levels in 51 hospitalized patients aged between 34 and 81 years. Four groups were defined: patients with SBP (group 1, n = 14), patients with bacteremia (group 2, n = 11), patients with urinary tract infection (group 3, n = 11) and patients in a stable clinical condition (group 4, n = 20). The four groups did not differ in terms of Pugh score (11 +/- 1, 10 +/- 1, 11 +/- 1, and 10 +/- 1, respectively). Serum nitrate levels averaged 31 +/- 2 micromol/L in group 4 (84 samples). On the day results of cytobacteriological examination were positive, mean serum nitrate levels were 75 +/- 17, 63 +/- 9, and 36 +/- 9 micromol/L, respectively, in groups 1 (17 cases), 2 (11 cases), and 3 (11 cases) (P < .001). The maximum nitrate values recorded during follow-up were higher in groups 1 (149 +/- 15 micromol/L) and 2 (112 +/- 11 micromol/L) than in group 3 (66 +/- 7 micromol/L; P < .001 and < .01, respectively). These maximum values were recorded in all groups approximately 2 weeks after the infection was diagnosed. The mean duration of NO overproduction, as defined by nitrate level (3)90 micromol/L, was 15 +/- 3 days in group 1 and 5 +/- 1 day in group 2. When the nitrate concentration was studied in serum and ascitic fluid sampled on the same day, it was found to be higher in ascitic fluid than in serum in eight cases of SBP in the period preceding the peak serum nitrate concentration (100 +/- 17 vs. 63 +/- 14 micromol/L; P < .001). Our data indicate that SBP in cirrhotic patients led to a long-lasting increased local production of NO. This overproduction may contribute to maintaining splanchnic vasodilation and thus worsen the hyperkinetic state in these patients.

N-3 fatty acids and urinary excretion of nitric oxide metabolites in humans

Fish oils rich in n-3 fatty acids have been shown to augment endothelium-dependent vasodilation in human peripheral and coronary arteries. This suggests that n-3 fatty acids may enhance arterial nitric oxide production. To explore this hypothesis we measured total urinary nitrate output in healthy volunteers supplemented with a fish oil concentrate (FOC; n = 15) or purified eicosapentaenoic acid (EPA; n = 14) in a placebo-controlled, parallel-group study. The FOC contained 41% EPA and 23% docosahexaenoic acid (DHA) ethyl esters, whereas EPA was 91% pure; the placebo contained olive oil ethyl esters. Doses were 5 g placebo, 5 g FOC, and 3 g EPA to keep the total n-3 fatty acid content equal in the latter two groups. The placebo period was 2 wk long and was followed by a 3-wk n-3 fatty acid phase. At the end of each period, 24-h urine collections and fasting blood samples were obtained. Serum and urinary nitrate concentrations were measured in a blinded fashion. The FOC produced a 43% increase in daily, creatinine-adjusted, nitrate excretion rates (P < 0.029). Because serum nitrate concentrations were not different, these findings suggest that FOC supplementation may stimulate systemic nitric oxide synthesis. The lack of effect with EPA supplementation suggests that this component of the FOC is not likely to be an active component. If confirmed, these observations suggest another mechanism whereby n-3 fatty acids may be antiatherogenic.

L-arginine augments nitric oxide production and mesenteric blood flow in ovine endotoxemia.

We studied the effects of administrating the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), or the nitric oxide precursor, L-arginine, on hemodynamic variables and serum nitrate concentrations in an anesthetized ovine model of endotoxemia to assess the effects on regional visceral blood flow and to determine whether L-arginine availability limits nitric oxide production. Animals received Escherichia coli endotoxin (2 micrograms/kg) followed 2 h later by L-NAME (25 mg/kg), L-arginine (0.575 g/kg), or saline administered over 1 h followed by an infusion of the same dose over 8 h (n = 6 per group). Renal and mesenteric blood flow were measured by placement of electromagnetic flow probes, and serum nitrate concentrations were determined using vanadium III chloride or nitrate reductase reduction to nitric oxide or nitrite, respectively. The results showed L-NAME significantly increased systemic vascular resistance (P < 0.01), decreased serum nitrate concentrations (P < 0.05), and caused a transient reduction in mesenteric blood flow (P < 0.05). L-Arginine caused a reduction in systemic vascular resistance (P < 0.01), increased mesenteric blood flow (P < 0.001) and conductance (P < 0.05). There were no significant changes in renal arterial blood flow in either group. We conclude that the availability of L-arginine limits nitric oxide production in endotoxemia and, furthermore, that L-arginine administration in this model causes significant mesenteric vasodilatation. L-NAME administration had only limited effect on visceral blood flow despite a marked increase in systemic vascular resistance and a reduction in nitric oxide production.

Systemic Hemodynamics and Serum Nitrate Levels in Patients Undergoing Endoscopic Variceal Ligation

The effects of endoscopic variceal ligation (EVL) on systemic hemodynamics are unknown. This study was conducted to determine whether the obliteration of portal–systemic collaterals by EVL affects systemic hemodynamics and serum nitrate concentrations in patients with compensated cirrhosis. We measured systemic and hepatic hemodynamics, azygos vein blood flow (AzBF), and serum nitrate concentrations before and immediately following EVL. A prompt decrease in left ventricular end–diastolic volume (LVEDV), stroke volume, cardiac index (CI), and an increase in systemic vascular resistance index (SVRI) were observed following variceal ligation. The reduction in LVEDV was associated with a decline in CI with a rise in SVRI. There was also a prompt reduction in serum nitrate concentration following variceal ligation. AzBF also significantly decreased following variceal ligation. These findings indicate that EVL decreased cardiac output via a reduction in cardiac preload (central venous return). Blood flow through portal–systemic collaterals has an important role in the enhanced cardiac preload of cirrhotic patients. The sudden decrease in serum nitrate concentrations suggests that endogenous nitric oxide may be involved in the regulation of systemic hemodynamics in patients with compensated cirrhosis.

Systemic hemodynamics and serum nitrate levels in patients undergoing endoscopic variceal ligation

The effects of endoscopic variceal ligation (EVL) on systemic hemodynamics are unknown. This study was conducted to determine whether the obliteration of portal-systemic collaterals by EVL affects systemic hemodynamics and serum nitrate concentrations in patients with compensated cirrhosis. We measured systemic and hepatic hemodynamics, azygos vein blood flow (AzBF), and serum nitrate concentrations before and immediately following EVL. A prompt decrease in left ventricular end-diastolic volume (LVEDV), stroke volume, cardiac index (CI), and an increase in systemic vascular resistance index (SVRI) were observed following variceal ligation. The reduction in LVEDV was associated with a decline in CI with a rise in SVRI. There was also a prompt reduction in serum nitrate concentration following variceal ligation. AzBF also significantly decreased following variceal ligation. These findings indicate that EVL decreased cardiac output via a reduction in cardiac preload (central venous return). Blood flow through portal-systemic collaterals has an important role in the enhanced cardiac preload of cirrhotic patients. The sudden decrease in serum nitrate concentrations suggests that endogenous nitric oxide may be involved in the regulation of systemic hemodynamics in patients with compensated cirrhosis. (Hepatology 1996 Jul;24(1):47-52)

Increased serum nitrate concentration in cardiac transplant patients. A marker for acute allograft cellular rejection.

The purpose of the present study was to investigate whether nitrate serum level, reflecting total body production of nitric oxide in vivo, could serve as a noninvasive marker for acute human cardiac rejection. Serum nitrate concentration was determined by an enzymatic method. During routine right ventricular endomyocardial biopsies in 59 recipients, 145 tissue samples were obtained. Two groups of biopsy specimen were considered on the basis of posttransplant delay: group 1, < or = 90 days (n=47; 12-90 days); and group 2, >90 days (n=98; 3-81 months). All patients had normal ventricular systolic function on the day of biopsy and none had evidence of infection. Rejection grade correlated closely with serum nitrate concentration (P<0.001). In both groups, nitrate serum concentrations differed significantly (P<0.001) among cases without rejection, those with mild ongoing rejection (grade 1A/1B), and those with focal or diffuse aggressive infiltrates (grade 2 or higher). A cutoff value of 20 micromol/L, was determined that was positively predictive for grade 2 or higher rejection in 62% cases of early episodes of rejection and in 68% cases of late rejection. Conversely, a serum nitrate level below 20 micromol/L was negatively predictive in 97% and 94% of early and late cases, respectively. We conclude that the acute rejection process of the human transplanted heart is accompanied by a significant increase in serum nitrate level, reflecting increased nitric oxide production during the immune response. Because of its high negative predictive value, irrespective of the posttransplantation delay, nitrate serum determination may have clinical utility in the noninvasive monitoring of the cardiac transplant patient and could also add important information to endomyocardial biopsy analysis for treatment decision making.

Serum Nitrite Plus Nitrate in Infection with Human Immunodeficiency Virus Type-1

To get a measure of the extent of induction of nitric oxide synthase in infection with human immunodeficiency virus type 1 (HIV-1) in vivo, we estimated serum nitrite plus nitrate concentrations in 110 HIV-1 infected individuals compared to 76 blood donors. To monitor cytokine action and to measure induction of pteridine synthesis, we determined in parallel neopterin, biopterin, soluble tumor necrosis factor-alpha receptor 55 and 75, β2-micro globulin. Serum nitrite plus nitrate concentrations were elevated in patients as compared to blood donor controls. In sera of patients, nitrite plus nitrate levels correlated significantly with neopterin, soluble tumor necrosis factor receptor 55 and 75, β2-microglobulin. Nitrite plus nitrate levels were higher and correlations were stronger in groups of patients with lower CD4+ cell count. These results suggest that cytokine-mediated nitric oxide synthesis occurs in individuals with HIV-1 infection.