The Nitrate / Nitrite Determination Kit is recommended for the determination of nitrite and nitrate, which is a method for the detection of nitric oxide formation.
The assay described here measures the nitrite and nitrate anions.

The detection is based on the final product detection (diazonium compound, λmax= 540 nm) obtained after nitrite reaction in several steps with sulfanilamide.

Firstly, the nitrate is reduced to nitrite, catalyzed by the nitrate reductase, with cofactors and specific compounds to eliminate interferences*. This step is very important  to eliminate interference.

Nitric oxide is an important molecular messenger in the vascular and nervous systems.
It has multiple physiological roles, such as vasorelaxation or neuronal signaling, but it also has other complex pathophysiological effects. The three isoforms of the nitric oxide synthases (eNOS, nNOS and iNOS) synthesize this molecule from L-arginine in the endothelial cells, neurons, macrophages, etc. In biological systems it decomposes to nitrite and nitrate.

The overproduction of nitric oxide may lead to oxidative and nitrosative stress. According to literature, they enhance the development of a variety of diseases, as well as the ageing process.

In addition, regarding nitrosative stress, high levels of iNOS are present in various inflammatory diseases such as arthritis and obesity. Furthermore, there is a relation between higher levels of NO and other cardiovascular diseases.