Background: 

Stent implantation into atherosclerotic saphenous vein aortocoronary bypass grafts releases, apart from particulate debris, soluble vasomotor substances (notably serotonin and thromboxane) and TNFa. TNFa levels impairs endothelial function and thus potentially its capacity to antagonize vasoconstriction. We therefore now determined the influence of TNFa on the vasoconstriction by serotonin and thromboxane.

Methods: 

In a bioassay, rat mesenteric arteries with denuded and intact endothelium were exposed to plasma of human healthy volunteers (n=12). After stabilization, a combination of the vasoconstrictors serotonin (3.5mM) and thromboxane(140pM) was added with / without TNFa (3pM). Vasomotion was measured over 10 min and normalized to that by potassium chloride (KCl_max = 100%).

Results: 

Arteries constricted after addition of serotonin and thromboxane; a stable maximum in vasoconstriction was reached within 2 to 4 min. Vasoconstriction was greater in vessels with denuded endothelium. TNFa potentiated the vasoconstriction in vessels with intact endothelium, but not in vessels with denuded endothelium.

Values are mean±SEM. ^#P<0.001 vs with denuded endothelium, *P<0.03 vs without TNFa. Statistical comparison was made by two-way analysis of variance with Bonferronni correction.

Conclusion: 

TNFa impairs endothelial function and therefore potentiates the vasoconstriction by serotonin and thromboxane.

	vasoconstriction of rat mesenteric arteries
	with intact endothelium (% of KClmax)	with denuded endothelium (% of KClmax)
serotonin + thromboxan without TNFa	109±6 #	143±6
serotonin + thromboxane with TNFa	133±10 #,*	132±5