Vascular function of organic nitrates in wild-type and ALDH-2−/− aortic rings and tachyphylaxis (in vitro tolerance). Concentration–relaxation response curves for 2-nitrooxyethylammoniumnitrate (AEN) (10−10 to 10−3.5 M; A and B), triethanolamine trinitrate (TEAN) (10−7 to 10−3 M; C and D) and methyl-3-nitrooxypropanoat (NPME) (10−7 to 10−3 M; E and F) were obtained by isometric tension recordings in aortic segments from wild-type (B6 WT) and ALDH-2−/− (ALDH-2 ko) mice. (A, C and E) Potency of the nitrates was compared in aorta from wild-type and ALDH-2−/− mice. (B, D and F) Effect of repeated concentration–relaxation response curves was tested resulting in pre-incubation of the rings with the EC70 (100 µM for AEN, 1 mM for TEAN and NPME). For both strains the first concentration–relaxation response curves and the subsequent are shown. (G) Comparison of the vasodilator potency of AEN, TEAN, glyceryl trinitrate (GTN) and NPME in B6 WT mice. Data are mean ± SEM of 14–30 independent experiments with tissue from 8–17 animals per group. *P < 0.05 versus WT on the same treatment. For further statistical analysis, see Table 1.