Interleukin-1 impairs both vascular contraction and relaxation in rabbit isolated aorta.

Incubation of rabbit aortic rings with interleukin-1 (100 U/ml) in vitro led to a depressed contractile response to norepinephrine, whether the endothelium was present or not. In both cases norepinephrine-induced contraction was restored in the presence of NG-methyl-L-arginine (300 microM), an inhibitor of nitric oxide synthesis. In interleukin-1-treated rings precontracted with norepinephrine (1 microM), the relaxing response to acetylcholine was totally suppressed independently on the presence of endothelium. High concentrations of acetylcholine (greater than 1 microM) induced a slight contraction which was of lower amplitude than that obtained in control endothelium-denuded rings and was increased in the presence of NG-methyl-L-arginine. These results show that interleukin-1 (i) affects not only vascular contraction but also relaxation and (ii) involves both endothelial and non-endothelial factors. These observations suggest an impairment of the whole vascular reactivity during septic shock.