Activation of caspase-9 (⧫) and caspase-3 (▪) by NO in APO-S Jurkat cells. Cells were treated for different periods of time with 0.2 mmol/L GTN. Cell lysates were then prepared and incubated with fluorogeneic peptides: LEHD-AFC (for caspase-9) and DEVD-AMC (for caspase-3). The products of reaction AFC or AMC were measured after 1 hour of incubation using a plate reader. Each point represents the mean ± SD of three independent experiments.