Effect of sildenafil treatment on the endothelial function. Acetylcholine-induced relaxation of mesenteric arterial bed preconstricted using norepinephrine, comparing 2K1C mice treated with sildenafil with non-treated 2K1C hypertensive and sham control mice (A and B). Bar graphs show the area under the curve (C), the maximum relaxation (Rmax) (D) and the sensitivity (pEC50) (E). Values are the means±SEM for 8–10 animals per group. **p < 0.01, one- (C, D and E) and two-way (A and B) ANOVA.