Nitric oxide (NO) plays an important role in neurotransmission, vascular regulation, immune response and apoptosis. Since NO is rapidly converted to nitrite (NO²ˉ) and nitrate (NOᶟˉ), the total concentration of nitrite and nitrate is used as a quantitative measure of NO production. BioVision’s Nitric Oxide Fluorometric Assay Kit provides an accurate and convenient measurement of total nitrate/nitrite concentration in a simple two-step process. In the first step nitrate is converted to nitrite by nitrate reductase. In the second step, nitrite reacts with the fluorescent probe DAN (2, 3 diaminonaphthalene). NaOH enhances the fluorescent yield. The fluorescent intensity is proportional to the total nitric oxide production. The kit has been tested with culture media, plasma, and tissue homogenates.