Fig. 3.

NOS2 S-nitrosylates arginase and regulates its activity in aging endothelium. A: arginase inhibition with BEC leads to improved endothelium-dependent vasodilation in old rat tail artery. acetylcholine, ACh concentration. B: arginase inhibition also restores NO production in old rat aorta as measured by diaminofluorescin (DAF) fluorescence C: NOS2 is expressed in old rat aorta, including importantly in the endothelium. iNOS, inducible NOS. D: arginase activity is significantly higher in old rat aorta than young (n = 4) and largely confined to the endothelium, because the endothelium-denuded rings show markedly reduced activity. Treatment of old vessels with the NOS2 inhibitor N-[3-aminomethylbenzyl]acetamidine (1400W) for 16 h leads to significant reduction (*P < 0.05) in arginase activity in old but not in young rats. D: endothelium-denuded rings are unaffected by 1400W. [From Santhanam et al. (71).]