2.5.3. Nitric Oxide
Nitric oxide was determined by nitrate/nitrite concentration using a fluorometric assay kit (Abcam ab65327, Cambridge, UK) following manufacturer instructions. Serum samples were filtered with a 10 kDa Spin column (Abcam ab93349, Cambridge, UK) to deproteinize the samples before the analysis. The analysis consisted of a two-step process: first, nitrate is converted to nitrite by nitrate reductase, and then nitrite reacts with the fluorescent probe 2,3 diaminonaphthalene. A nitrite standard calibration curve was used to compare the fluorescence intensity of samples. The analysis was performed in triplicate in each sample.