Cellular ROS levels and relative LDH activities. (a) ROS production monitored by ESR spectroscopy. 3 × 106 cells/ml SMMC 7721 hepatoma cells (Panel a) or L02 liver cells (Panel b), or SOD-transfected 7721 cells (Panel c), or antisense-SOD-transfected 7721 cells (Panel d) were incubated with BMPO (100 mM). ROS production was assessed by ESR spectroscopy as described under "Materials and methods". In panel (e) SMMC-7721 cells were treated as in panel (a) with SOD (100 U/mL). The present spectrums are representative of three experiments. (b) Comparison of cellular LDH activity. LDH activity levels in SMMC-7721 cells, L02 cells, SOD-transfected 7721 cells (SOD-7721) and antisense-SOD-transfected 7721 cells (SOD-AS7721) were measured as described in "Materials and methods". LDH activity was expressed relative to control SMMC-7721 cells. Columns: * P < 0.05 versus control SMMC-7721 cells. The values represent the means ± S.D. from four independent experiments.