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Figure 6 Endothelial Cell NO Generation and Vasodilation

(A) Basal endothelial production of nitrite and nitrate is generated by incubating endothelial cells with L-arginine, the substrate of nitric oxide synthase (NOS), in the presence of test serum/HDL (50,88–90). Stimulated production is achieved through simultaneous addition of an NOS agonist, such as A23187. To stimulate endothelial production of free radicals, endothelial cells are incubated with an NOS inhibitor, such as L-nitroarginine-methylester (L-NAME), thereby inhibiting free-radical scavenging capacity, and the concentration of O2– is measured. Using this cell-based assay, enhanced NOS activity, nitric oxide (NO) production, and diminished O2– generation achieved by the test serum/HDL suggest restorative effects on endothelium and thus an antiatherogenic benefit. (B) The apoA-I mimetic L-4F restores NO production in cultured endothelial cells coincubated with LDL in the presence or absence of the NOS agonist A23187 (90). Reprinted, with permission, from Ou et al. (90). Figure illustrations by Rob Flewell. eNOS = endothelial nitric oxide synthase; other abbreviations as in Figures 1 and 2.