Fig. 3. H₂O₂-induced apoptotic cells display NOS-like activity. (A) NOS activity assessed in untreated and H₂O₂-treated wild-type cells. The radioactivity obtained from a negative control consisting of yeast extract boiled for 20 minutes was subtracted from all the samples to remove background radioactivity. Data are expressed as the percentage conversion of L-[³H]arginine to [³H]citrulline. ^*P0.03 versus untreated cells; t-test, n=4. (B) Intracellular amino acid concentrations of untreated (control) and H₂O₂-treated wild-type cells. ^*P0.05 versus untreated cells; t-test, n=3.