HHcy-impaired endothelium-dependent and EDHF-mediated relaxation occurs via oxidative stress in SMAs of Tg-hCBS Cbs mice. (A-F) Endothelium-dependent relaxation response to cumulative concentrations of ACH in SMAs pretreated with indicated inhibitors for 1 hour. (G-L) EDHF-mediated relaxation to cumulative additions of ACH in SMAs pretreated with indicated inhibitors for 1 hour, and with the COX inhibitor INDO (1μM) plus the NOS inhibitor L-NAME (100μM) for another 30 minutes. (M) ONOO⁻-inhibited EDHF-mediated relaxation in SMAs of control mice. EDHF-mediated relaxation to cumulative concentrations of ACH was assessed in SMAs pretreated without and with ONOO⁻ (100μM) for 30 minutes, followed by the SK/IK opener NS309 (1μM) in the presence of INDO and L-NAME for an additional 30 minutes. (N) The SK/IK opener NS309 restored EDHF-mediated relaxation in Cbs^−/− mice. EDHF-mediated relaxation to cumulative concentrations of ACH was assessed in SMAs pretreated with the SK/IK opener NS309 (10μM) in the presence of INDO and L-NAME for 30 minutes. (O) ONOO⁻-inhibited SK/IK opener-mediated relaxation in SMAs of control mice. Vascular relaxation response to cumulative additions of NS309 (10nM-10μM) was assessed in SMAs pretreated without and with ONOO⁻ (100μM) for 30 minutes followed by INDO and L-NAME for an additional 30 minutes. SMAs were precontracted with PE (1μM). Values are means ± SEM (n = 5-7 mice). *P < .05 compared with control mice in the experiment shown in Figure 1D and G; †P < .05 compared with CBS^−/− mice in Figure 1D and G; and ‡P < .05 compared with the NS309-treated group in Figure 1D and G. CT indicates the control group.