NG-nitro-L-arginine (N5-[imino(nitroamino)methyl]-L-ornithine) impairs endothelium-dependent dilations by inhibiting cytosolic nitric oxide synthesis from L-arginine.
We studied the effects of the L-arginine analogue NG-nitro-arginine (L-NNA), in comparison with its D-isomer [D-NNA), on endothelium-dependent dilations of rabbit femoral arteries (RFA) and on the release of endothelium-derived relaxant factor (EDRF) from native and cultured endothelial cells. In addition, we examined the effects of L- and D-NNA on the L-arginine- and NADPH-dependent synthesis of nitric oxide (NO) in the cytosol of porcine aortic endothelial cells. L-NNA enhanced the noradrenaline-induced contraction of endothelium-intact, but not of endothelium-denuded segments of RFA, indicating an inhibition of basal EDRF release. L-NNA also inhibited significantly the endothelium-dependent dilations to acetylcholine (ACh). Both effects of L-NNA were attenuated by L-arginine. L-NNA rapidly inhibited the release of EDRF from cultured and native endothelial cells stimulated with thimerosal or ACh. L-NNA concentration-dependently and reversibly antagonized the L-arginine- and NADPH-dependent activation of a purified soluble guanylate cyclase (GC) by cytosol from freshly harvested porcine aortic endothelial cells, suggesting a direct competition between L-NNA and L-arginine at the level of endothelial NO-synthesis. D-NNA was ineffective in all instances. These results prove L-NNA to be a stereospecific inhibitor of the cytosolic NO formation from L-arginine in endothelial cells. Therefore, L-NNA will be a useful tool to elucidate the molecular mechanism of mammalian NO synthesis.
Mülsch
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A
Department of Applied Physiology, University of Freiburg, Federal Republic of Germany.
Busse
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R
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D005263:Femoral Artery / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D019335:Nitroarginine; D011817:Rabbits; D013237:Stereoisomerism; D013552:Swine; D014664:Vasodilation / Q000187:drug effects*
D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine; D000109:Acetylcholine