A549 stimulation nitric oxide
 

Dear members,

I have problems with stimulating A549 cells to produce measurable amounts of nitric oxide. I tried different combinations of cytokines, also LPS 1microg/mL+IFN-gamma 100ng/mL+TNF-alpha 100ng/mL+IL-1beta 100ng/mL without any success.
I use the griess assay to measure nitrite after 18h of stimulation.
Has anyone experience or advice concerning that issue?

Thanks a lot for help in advance.