Administration of tumor necrosis factor-alpha in vivo depresses endothelium-dependent relaxation.
Although depressed endothelium-dependent relaxation occurs during early sepsis, the precise mechanism responsible for this remains unknown. Because the elevated levels of plasma tumor necrosis factor (TNF) play a major role in the pathophysiology of sepsis, we investigated whether TNF-alpha administration alters endothelium-dependent relaxation. To study this, recombinant TNF-alpha (1.2 x 10(7) U/mg) was infused intravenously (0.25 mg/kg body wt) for 0.5 h in normal rats, and mean arterial pressure was monitored. At 1 h after the completion of TNF-alpha or vehicle infusion, the aorta and a pulmonary artery were isolated, cut into 2.5-mm rings, and placed in organ chambers. Norepinephrine (2 x 10(-7) M) was applied to achieve near-maximal contraction, and dose responses for an endothelium-dependent vasodilator, acetylcholine, and an endothelium-independent vasodilator, nitroglycerine, were determined. In additional studies, aortic rings from normal animals were incubated with TNF-alpha for 2 h in vitro, and vascular reactivity was determined. The results indicate that TNF-alpha administration significantly reduced acetylcholine-induced vascular relaxation both in vivo and in vitro. Such a reduction was sustained at least 80 min after the completion of 2-h incubation with TNF-alpha. In contrast, TNF did not alter nitroglycerine-induced vascular relaxation. Thus TNF-alpha depresses endothelium-dependent relaxation in vitro as well as in vivo. Because TNF-alpha infusion increases plasma TNF levels without decreasing mean arterial pressure, the depressed endothelium-dependent relaxation observed during early sepsis may be due to the elevated circulating levels of TNF.
Wang
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Department of Surgery, Michigan State University, East Lansing 48824.
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D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects; D004730:Endothelium, Vascular / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D005996:Nitroglycerin / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D014661:Vasoconstriction; D014664:Vasodilation / Q000187:drug effects*
D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D005996:Nitroglycerin; D000109:Acetylcholine; D009638:Norepinephrine