Superoxide anion production in mesenteric vascular beds. Top panel shows representative histograms from flow cytometric analysis using dihydroethidium (DHE), diaminofluorescein (DAF) and hydroxyphenyl fluorescein (HPF) in Sham, 2K1C hypertensive and sildenafil-treated 2K1C mice; the log fluorescence (X axis) illustrates the differences in intensity of fluorescence for the number of cells counted. Bar graph shows augmented production of superoxide anions and peroxynitrite in 2K1C hypertensive mice compared with Sham mice and sildenafil treatment restored the normal values. On the other hand, 2K1C mice presented impairment of nitric oxide production compared with sham mice, and sildenafil treatment restored the normal levels. Values are median fluorescence intensity (MFI, in arbitrary units) ± SEM for 5 animals per group. *p < 0.05 (one-way ANOVA).