Inhibition of endothelial nitric oxide biosynthesis by N-nitro-L-arginine

1. The actions of N-nitro-L-arginine (NOLA) on the release of nitric oxide (NO) from arterial endothelial cells was studied in rat isolated thoracic aortic rings and by bioassay of NO derived from cultured bovine aortic endothelial cells. 2. NOLA (3-10 mumol/L) caused concentration-dependent inhibition of acetylcholine-induced relaxation of phenylephrine-contracted rat aortic rings, which is dependent on the release of NO from the endothelium. The inhibitory actions of NOLA could be prevented by pre- and co-incubation with L-arginine (1 mmol/L). 3. Endothelium-independent relaxation induced by sodium nitroprusside was not affected by NOLA. 4. The release of NO from bovine aortic endothelial cells, induced by bradykinin (10 nmol/L), was detected by bioassay on pre-contracted rabbit aortic strips. NOLA (1-3 mumol/L, given through the cell column) reduced or abolished the release of NO, but did not affect relaxations of the bioassay tissues induced by glyceryl trinitrate or authentic NO. 5. These data indicate that NOLA potently inhibits the biosynthesis of NO from L-arginine, and thus prevents its release from arterial endothelial cells. It may be a useful pharmacological tool for probing the significance of NO biosynthesis in cardiovascular function.