Measurement of nitric oxide production

Nitrite concentrations in the media were measured using the Griess reaction [²³]. Briefly, media samples were collected from each well following appropriate treatment and reacted with modified Griess reagent by mixing equal volumes with each other at room temperature for 15 minutes. Optical density was then measured and read on a multi-well scanning spectrophotometer at 540 nm. The nitrite concentration was then determined from a comparison of absorbance with that of a standard solution of sodium nitrite in medium. The background absorbance, measured using the medium alone, was subtracted from all values.