Measurement of NO in biological samples

Abstract

Although the physiological regulatory function of the gasotransmitter NO (a diatomic free radical) was discovered decades ago, NO is still in the frontline research in biomedicine. NO has been implicated in a variety of physiological and pathological processes; therefore, pharmacological modulation of NO levels in various tissues may have significant therapeutic value. NO is generated by NOS in most of cell types and by non-enzymatic reactions. Measurement of NO is technically difficult due to its rapid chemical reactions with a wide range of molecules, such as, for example, free radicals, metals, thiols, etc. Therefore, there are still several contradictory findings on the role of NO in different biological processes. In this review, we briefly discuss the major techniques suitable for measurement of NO (electron paramagnetic resonance, electrochemistry, fluorometry) and its derivatives in biological samples (nitrite/nitrate, NOS, cGMP, nitrosothiols) and discuss the advantages and disadvantages of each method. We conclude that to obtain a meaningful insight into the role of NO and NO modulator compounds in physiological or pathological processes, concomitant assessment of NO synthesis, NO content, as well as molecular targets and reaction products of NO is recommended.

Nitric oxide synthetic pathway and cGMP levels are altered in red blood cells from end-stage renal disease patients

“…Analysis of NO content was performed with double integration of the NO signal as described previously [34][35][36]. NO content of the samples were expressed in arbitrary units as this method enables a semi-quantitative assessment of NO content in biological samples (see for review Csonka et al [37]). …”

Quantification of nitric oxide by high‑performance liquid chromatography‑fluorometric method in subgenomic hepatitis C virus‑replicon expressing Huh7 cells upon treatment with acetylsalicylic acid

“…Hepatocytes produce NO in picomolar levels (6), therefore it is difficult to detect and quantify NO levels within them. In the present study, the HPLC-fluorescence detector method was employed.…”

“…The Griess reaction is inexpensive, simple and fast; however, the limit of detection is ~0.5 µM, which restricts the application of this colorimetric method for quantifying micromolar, nanomolar and picomolar levels of NO 2 -, and therefore physiological amounts (6). Furthermore, the media composition in biological systems may alter the measurements of NO due to the presence of other proteins, such as hemoglobin, which is also detected at 540 nm (7).…”

Is nitrate a good biomarker of the nitric oxide status? / Este ionul nitrat un bun biomarker al producţiei endogene de monoxid de azot?

“…Its importance for biomedical research is owing to: (a) it is a free radical found in all tissues, (b) it is involved in a large number of physiological and pathological processes, (c) NO donors are used in clinical therapy and new molecules with the ability to release NO are under constant demand (1). NO concentrations are particularly important since, as with any messenger molecule, too little or too much of the substance can result in pathological events (2,3).…”