How to make THP-1 and Jurkat cells to produce nitric oxide??

Hello everyone,

I'm trying to make my THP-1 (human monocitic/macrophage cell line) and
Jurkat (human T cell leukemia) cells to produce nitric oxide. I've tried LPS
for THP-1 and LPS and PHA-L for Jurkat cells but I've got nearly nothing.
Adversely,  I found papers claiming that LPS activated THP-1 and Jurkat
cells produce NO in micro molar range after 24 hours, but the production
I've found was just up to 5nM. The quantity of NO was assessed using Griess
reagent with cell supernatants and the absorbance was measured at 548 nm. 

If you have any ideas, suggestions or maybe even solutions I would be
extremely grateful:-)

Adriana.

       _______

Adriana Lepur, M.pharm.

University of Zagreb

Faculty of Pharmacy and Biochemistry

A. Kovacica 1, Zagreb

Croatia.