Simultaneous analysis of nitrite, nitrate and the nicotinamide nucleotides by capillary electrophoresis: Application to biochemical studies and human extracellular fluids

Abstract

A simple but rapid capillary electrophoresis method was developed for the measurement of nitrite and nitrate in human extracellular fluids and other aqueous solutions. The capabilities of the method were demonstrated by the measurement of endogenous nitrite and nitrate in plasma and serum samples from healthy volunteers, and serum and synovial fluid samples from rheumatoid arthritis patients. Furthermore, this method was used to simultaneously measure nicotinamide adenine dinucleotide, reduced (NADH), nicotinamide adenine dinucleotide (NAD+), nitrite, and nitrate, when studying the nitrite reductase activity of xanthine oxidase. The stability of nitrite was also investigated and it was found that when whole blood was spiked with nitrite and then processed, the nitrite was more stable in the plasma than in the serum. Our findings may help to explain the variations in basal nitrite concentrations reported in the literature.

Inhibition of hypochlorous acid-induced cellular toxicity by nitrite

“…There is considerable evidence that HOCl and the end products of ⅐NO metabolism (NO 2 Ϫ and NO 3 Ϫ ) accumulate at sites of chronic inflammation (1,2,(33)(34)(35)(36). HOCl is known to oxidize many important classes of biomolecules (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) as well as chlorinate protein, DNA, and cholesterol (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26) and cause cell death (12).…”

Nitrite‐mediated protection against hypochlorous acid–induced chondrocyte toxicity: A novel cytoprotective role of nitric oxide in the inflamed joint?

“…Under physiologic conditions, NO oxidizes to form stable end products of NO metabolism that accumulate as nitrite (NO 2 Ϫ ) and nitrate (NO 3 Ϫ ) (48). Increased levels of these metabolites, as an index of increased NO synthesis, have been measured in several chronic inflammatory diseases, such as RA (49)(50)(51)(52)57) as well as other rheumatoid conditions, including systemic lupus erythematosus (60), systemic sclerosis (58), and Sjögren's syndrome (55,57), where sera and plasma concentrations of NO 2 Ϫ Figure 5. HOCl-mediated chondrocyte lipid peroxidation: effect of NO 2 Ϫ .…”

“…] and nitrate [NO 3 Ϫ ] [48]) have been detected in sera, plasma, and synovial fluids (49)(50)(51)(52)(53)(54) of affected patients. In addition to invading inflammatory phagocytes, cells within the human joint, such as articular chondrocytes, pannocytes, synovial fibroblasts, synovial macrophages, osteoblasts, and osteoclasts, are capable of synthesizing M quantities of NO, contributing to the elevated levels of NO 2 Ϫ observed (for review, see refs.…”

“…However, significantly elevated levels have been detected in patients with inflammatory diseases, e.g., serum NO 2 Ϫ levels have been reported to reach mM concentrations in patients with RA (57), systemic sclerosis (58), Sjögren's syndrome (59), and systemic lupus erythematosus (60). Levels of NO 2 Ϫ in synovial fluid of patients with RA are reported to range from 0.3 M to 15 M (48-51), with levels of NO 3 Ϫ substantially higher (49,(52)(53)(54)(55). Salivary NO 2 Ϫ levels in patients with Sjögren's syndrome have also been reported to reach Ͼ350 M (61), compared with ϳ98 M in healthy individuals (61,62).…”

Advances of capillary electrophoresis in clinical and forensic analysis (1999-2000)

“…The use of CE to determine these two ions in biological fluids has become popular. In the time period covered in this review, low-cost, simple and rapid assays for nitrite and nitrate were described by Bories et al [146], Zunic et al [147] and Davies et al [148], and, based upon data generated by CE, increased nitric oxide was determined for infective gastroenteritis [149], in neuropsychiatric lupus erythematosus [150] and in multiple sclerosis [151]. Finally, Tagliaro et al [152] described a new, simple and rapid capillary ion analysis method for the determination of potassium in human vitreous humor, an approach used for estimation of the postmortem interval.…”