NADPH oxidase activation in response to phenylephrine stimulation. (a) Time course. RTA strips were stimulated with 10 μM PE for the indicated period. NADPH oxidase activity was measured in RTA homogenates as described in Methods and was expressed as mean ± SEM of 5 independent experiments. *P< 0.05 vs. unstimulated control. (b) Effects of pro-oxidative enzyme inhibitors. RTA strips were incubated for 30 min with the indicated inhibitors, followed by 1-min phenylephrine stimulation. Results were expressed as mean ± S.E.M. of 6~8 independent experiments. *P < 0.05 vs. unstimulated control; #p < 0.01 vs. phenylephrine alone.