The concentration of NO was determined
using a colorimetric assay based on the Griess reaction. Fifty microlitters of
cell culture medium was collected and given 100 mL of Griess reagent (6 mg/mL) at
room temperature for 10 min, and then the NO concentration was determined by
measuring the absorbance at 570 nm using a microplate reader (E-Max, Molecular
Device Co, US).