Cell viability assay

The MTT assay was employed to quantify cell viability. Jurkat cells were washed once with RPMI-1640, and ~3×10⁵ cells were seeded to each sample. The cells were then cultured at 37°C for 6 h with different concentrations of L-NMMA (0, 0.25, 0.5, 1, 2 and 4 mM). At the end of the treatment, MTT reagent (5 mg/ml, 20 µl) was added to each sample and cells were incubated at 37°C for 3 h, DMSO (200 µl) was then added to each sample, in order to dissolve the cell precipitation. A total of 150 µl liquid was transferred to the well of a96-well plate and the optical density value of each well was determined using a plate reader at 570 nm.