Low dose of lipopolysaccharide induces a delayed enhanced nitric oxide-mediated relaxation in rat aorta

Delayed effect on vascular reactivity of isolated aorta was studied after i njection of a single low dose of lipopolysaccharide (0.5 mg/kg i.p.). The m aximal vascular effect was observed 72 h after lipopolysaccharide administr ation with an increase in maximal endothelium-dependent relaxing response t o acetylcholine and parallelly a decrease in contractile response to phenyl ephrine. The change in contractile response was nullified by endothelium re moval as well by in vitro aortic rings incubation with N-omega-monomethyl-L -arginine but not with indomethacin. A low dose of lipopolysaccharide induc es a delayed enhanced nitric oxide-mediated vascular relaxation which could contribute to its delayed anti-ischemic properties in ischemic tolerance p henomenon. (C) 1999 Elsevier Science B.V. All rights reserved.