NAADP levels. NAADP levels measured over time in EA.hy926 endothelial cells stimulated with 100μM TMPH and control cells. The absolute resting concentration of NAADP was 1.774 88 ± 0.65 pmol/mg protein. Where applicable, error bars represent SEM; n = 2-3 independent experiments; *P < .05 by Student t test.