Phenylephrine-stimulated superoxide anion generation. RTA strips were stimulated with 10 μM phenylephrine and superoxide anion generation was measured by lucigenin-enhanced chemiluminescence as described in Methods. Some vessels were incubated for 1 hr with α1-adrenoceptor antagonist prazosin (1 μM) or for 30 min with VAS2870 (10 μM), apocynin (1 mM), tiron (10 mM), indomethacin (10 μM), allopurinol (100 μM), rotenone (10 μM) or vehicle (DMSO or ethanol) before and during phenylephrine treatment. As the values obtained in the presence of DMSO or ethanol were not different from that of phenylephrine alone, the data were pooled. Each bar represents mean ± S.E.M. of six to ten independent experiments. *p < 0.001 vs. control; #p < 0.05 vs. vehicle.