Implication of steady state concentrations of nitrite and nitrate metabolites of nitric oxide in plasma and whole blood in healthy human subjects

Abstract

1. The aim of the present study was to determine whether the steady state NOx concentration reflects NOx formation in vivo. 2. A NO3- load study was performed after achieving NOx steady state. Chronological changes in NOx concentrations in plasma and whole blood samples from nine healthy subjects were determined by the HPLC-Griess system and NOx concentrations in erythrocytes were estimated as a possible NOx compartment influential in regulating plasma NOx concentrations. 3. Analysis was performed using the first-order one-compartment open model and the NOx formation rate was subsequently calculated. 4. The mean (+/-SEM) steady state NOx concentration of plasma (15.5 +/- 1.6 micromol/L), whole blood (12.8 +/- 1.2 micromol/L) and erythrocytes (11.9 +/- 0.7 micromol/L) did not correlate with the NOx formation rate in the compartments (0.50 +/- 0.05, 0.61 +/- 0.04 and 0.91 +/- 0.17 micromol/kg per h, respectively), whereas a significant correlation was found between the steady state NOx concentration and NOx elimination rate (Kel) in plasma (r=-0.69; P=0.04) and whole blood (r=-0.79; P=0.01). 5. Although there was no direct correlation between steady state NOx concentrations and serum creatinine levels, the correlation between half-life and serum creatinine levels was significant (plasma: r=0.60, P=0.02; whole blood: r=0.49, P=0.04). 6. Plasma NOx concentrations correlated significantly with erythrocyte NOx concentrations (r=0.92, P <0.01; erythrocyte NOx=0.66 x plasma NOx). 7. The results of the present study indicate that NOx does not accumulate excessively into erythrocytes at steady state and during a NO3- load and that the steady state NOx concentration in whole blood and plasma preferentially implies NOx elimination (mainly depending on renal function) rather than NOx formation.

Analysis of nitrite and nitrate in biological samples using high-performance liquid chromatography

“…The authors found that the steady-state plasma levels of NO x (15.5 ± 1.6 M, mean ± S.E.M.) were significantly correlated with renal function [59]. Using the same analytical method, Adachi et al [60] showed that patients with renal failure had higher levels of plasma nitrate compared with those with normal renal function (80.7 ± 44.2 M, n = 15 versus 21.6 ± 4.6 M, n = 14; mean ± S.D., P < 0.01).…”

“…When concentrations of nitrite and nitrate in urine are used as markers of whole-body NO synthesis under various physiological and pathological conditions, renal function and clearance should be considered. A nitrate load study was performed by Himeno et al [59] to evaluate a relationship between steady-state plasma concentrations of NO x and in vivo NO x formation or NO x clearance. Blood samples from nine healthy subjects were obtained for analyses of nitrite and nitrate using an HPLC-UV method.…”

C-reactive protein is associated with cigarette smoking-induced hyperfiltration and proteinuria in an apparently healthy population

“…Although the measurement of NO itself cannot be performed, nitrite (NO 2 À ) and nitrate (NO 3 À ) (NOx) are commonly used as an index of systemic NO formation in many studies, based on the finding that NOx is the main stable metabolite. 18 This study is the first attempt to employ an ozone-based chemiluminescence assay for detecting plasma NOx in a large, healthy population.…”

Quantifying Nanomolar Levels of Nitrite in Biological Samples by HPLC-Griess Method: Special Reference to Arterio-Venous Difference in vivo

“…Indeed, several studies have reported a close relationship among changes in endotheliumdependent blood flow, plasma NO 2 -levels (Lauer et al 2001;Kleinbongard et al 2003Kleinbongard et al , 2006, Kleinbongard et al 2003) compared with plasma levels of nitrates (NO 3 -) (Ishibashi et al 2000a;Himeno et al 2003), although the measurement may not necessarily be free from contamination. Measurements are therefore required to minimize possible NO 2 -contamination from laboratory ware and the environment to accurately determine the level of this ubiquitous substance in biological samples (Ishibashi et al 2000a;Himeno et al 2004). Many laboratories have stressed the importance of avoiding contamination in the enhancement of vasodilatory activity of NO 2 -and increased production of NO in the presence of deoxyHb (Cosby et al 2003;Lundberg and Govoni 2004;Crawford et al 2006;Grubina et al 2007;Shiva et al 2007).…”