Macrophages

A macrophage cell culture model can be used to assess the ability of the test materials to exert an effect on nitric oxide (NO) synthesis or release.  NO release by macrophages and lymphocytes can have cytotoxic effects and is often used by these immune cells to fight off infections agents such as bacteria.   For assay purposes the macrophages (murine RAW 264.7) are stimulated to produce nitric oxide by exposing them to lipopolysaccharide (LPS) and then measuring the amount of NO released over a 24 hour period in the presence of different test materials.  NO is a very short-lived compound which rapidly degrades into very stable end products: nitrite and nitrate. While the nitrite end product can be easily measured, the nitrate must be enzymatically converted to nitrite before it can be measured.  Total nitrite can then be assayed using a spectrophotometric technique based on the reaction of the nitrite and a Griess Reagent.