Nitric oxide release may be involved in the microcirculatory response to acetylcholine.
An image-splitter television microscope for measurement of microvascular dimension changes in the rat exteriorized mesentery was used to investigate the role of endothelium-derived relaxing factor (EDRF)/nitric oxide (NO) in the microcirculation. This was done by studying the effect of NG-monomethyl-L-arginine (L-NMMA), a specific inhibitor of NO formation, on the responses induced by acetylcholine (an endothelium-dependent vasodilator agent) and sodium nitroprusside (an endothelium-independent vasodilator agent). The effect of acetylcholine on mesenteric A2 arterioles was impaired by previous application of L- but not D-NMMA to the preparations whereas the vasodilator response to sodium nitroprusside was not altered. The effect of L-NMMA was slow to disappear, unless accelerated by a 3-fold molar excess of L- but not D-arginine. It is suggested that EDRF/NO might be involved in the vasodilator response to endothelium-dependent agents such as acetylcholine at the microcirculatory level and that L-arginine might be the physiological precursor of NO.
Department of Pharmacology, University of São Paulo, Brazil.
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D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001160:Arterioles / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology*; D009129:Muscle Tonus / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism* / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014664:Vasodilation / Q000187:drug effects; D019323:omega-N-Methylarginine
D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D000109:Acetylcholine; D009638:Norepinephrine