Acetylcholine-mediated vasodilatory responses in isolated mesenteric resistance arteries from HSD fed rats. Vasodilatory responses to acetylcholine (ACh) were measured in the presence and absence of the NOS inhibitor Nω-nitro-L-arginine (LNNA; 100 μM) in small mesenteric arteries (n = 6-8). Arteries were exposed to LNNA in the lumen and superfusate prior to pre-constriction with phenylephrine to 45-50% resting inner diameter. Vasodilatory responses to acetylcholine (ACh) were also measured in the presence and absence of antioxidants HSD (n = 4-9). For these studies, arteries were pre-exposed to the ROS scavengers 4,5-Dihydroxy-1,3-benzene-disulfonic acid (tiron; 10 mM) and catalase (1200 U/mL) or EUK-134 (10 μM). Separate arteries were exposed to the nitric oxide synthase inhibitor LNNA (100 μM) or LNNA with the addition of EUK-134 or tiron and catalase. The HSD control data (dotted line) are repeated from figure 2 for comparison.Data are expressed as means ± SEM. *p ≤ 0.05 HSD controls vs. Chow controls; #p ≤ 0.05 vs. HSD controls; † p < 0.05 vs. HSD EUK-134 or T+C only; §p ≤ 0.05 vs. HSD LNNA only.