Participation of tumour necrosis factor and nitric oxide in the mediation of vascular dysfunction in splanchnic artery occlusion shock

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Abstract
1 Splanchnic artery occlusion (SAO) shock is characterized by irreversible circulatory failure. Tumour necrosis factor (TNF-α) may affect the 1-arginine/nitric oxide (NO) pathway, thus contributing to the cardiovascular derangements of circulatory shock. 2 We investigated the contribution of both TNF-α and the 1-arginine/nitric oxide pathway to the vascular dysfunction of SAO shock. Anaesthetized rats, subjected to total occlusion of the superior mesenteric artery and the coeliac trunk for 45 min developed a severe shock state (SAO shock) resulting in a fatal outcome within 75–90 min after the release of occlusion. Sham operated animals were used as controls. SAO shocked rats had also a marked hypotension and enhanced macrophage and serum levels of TNF-α. Furthermore, aortic rings from shocked rats showed a marked hyporeactivity to phenylephrine (PE 1 nm-10 μm) and reduced responsiveness to acetylcholine (ACh lOnM-lOμm). Endothelium-denuded aortic rings had also a marked hyporeactivity to phenylephrine, which was restored to control values by in vitro administration of N° nitro-1-arginine-methyl ester (1-NAME 10 μm). 3 In vivo administration of cloricromene (2 mg kg−1, i.v.), an inhibitor of TNF-α biosynthesis, increased survival, enhanced mean arterial blood pressure and reduced macrophage and serum levels of TNF-α. Furthermore, aortic rings from shocked rats treated with cloricromene exhibited a greater contractile response to phenylephrine and improved responsiveness to ACh when compared to aortic rings from vehicle-treated SAO shocked rats. 4 Our results suggest that TNF-α alters both endothelial and muscular L-arginine/nitric oxide pathways which in turn produce vascular dysfunction in SAO shock.

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