Fig. 5.

Effect of antioxidants on PMET activity and insulin secretion. Following the 2-h preincubation period, INS-1 832/13 cells (A) or islets (B) were exposed to N-acetylcysteine (NAC, 0.4 mM), Trolox (0.5 mM), polyethylene glycol superoxide dismutase (PEG-SOD) (30 U/ml), and ascorbate (25 μg/ml). Dehydroascorbae (DHA, 250 μM) was present during the preincubation period to elevate intracellular ascorbate levels. The amount of WST-1-formazan was determined as described in materials and methods. Insulin secretion (C and D) and nucleotide ratios (E and F) were performed in parallel. Data are means ± SE from 2–4 independent experiments performed in triplicate measurements. *P < 0.05 compared with the corresponding control value.