TY - JOUR
T1 - Contractions to oxygen-derived free radicals are augmented in aorta of the spontaneously hypertensive rat
AU - Auch-Schwelk, Wolfgang
AU - Katusic, Zvonimir S.
AU - Vanhoutte, Paul M.
PY - 1989/6
Y1 - 1989/6
N2 - To determine if oxygen-derived free radicals are mediators of endothelium-dependent contractions to acetylcholine in the aorta of spontaneously hypertensive rats (SHR), the mechanism of contraction to xanthine plus xanthine oxidase was studied. Rings, with and without endothelium, of thoracic aorta from normotensive Wistar-Kyoto (WKY) rats and SHR were suspended in organ chambers for isometric tension recording. Oxygen-derived free radicals caused concentration-dependent contractions; these contractions were twice as large in the aortas of SHR than in WKY rats. Deferoxamine reversed the response to xanthine oxidase to a small relaxation. Either allopurinol, superoxide dismutase, or catalase, or the combination of superoxide dismutase plus catalase reduced the contractions. Diltiazem inhibited the response to xanthine oxidase; in contrast, phentolamine plus propranolol did not affect it. Indomethacin and meclofenamate, but not tranylcypromine or dazoxiben blocked the contractions. Endotheliumdependent contractions to acetylcholine in aortas from the SHR were not affected by deferoxamine or superoxide dismutase plus catalase. These data suggest that hydroxyl radicals cause contractions in the rat aorta, which are dependent on extracellular calcium and mediated by activation of the cyclooxygenase in the vascular smooth muscle. The augmented contractions in the hypertensive strain are due to an increased reactivity of the smooth muscle to oxygenderived free radicals. However, the lack of effect of the scavengers on endothelium-dependent contractions to acetylcholine suggests that the endothelium-derived contracting factor is chemically different from oxygen-derived free radicals.
AB - To determine if oxygen-derived free radicals are mediators of endothelium-dependent contractions to acetylcholine in the aorta of spontaneously hypertensive rats (SHR), the mechanism of contraction to xanthine plus xanthine oxidase was studied. Rings, with and without endothelium, of thoracic aorta from normotensive Wistar-Kyoto (WKY) rats and SHR were suspended in organ chambers for isometric tension recording. Oxygen-derived free radicals caused concentration-dependent contractions; these contractions were twice as large in the aortas of SHR than in WKY rats. Deferoxamine reversed the response to xanthine oxidase to a small relaxation. Either allopurinol, superoxide dismutase, or catalase, or the combination of superoxide dismutase plus catalase reduced the contractions. Diltiazem inhibited the response to xanthine oxidase; in contrast, phentolamine plus propranolol did not affect it. Indomethacin and meclofenamate, but not tranylcypromine or dazoxiben blocked the contractions. Endotheliumdependent contractions to acetylcholine in aortas from the SHR were not affected by deferoxamine or superoxide dismutase plus catalase. These data suggest that hydroxyl radicals cause contractions in the rat aorta, which are dependent on extracellular calcium and mediated by activation of the cyclooxygenase in the vascular smooth muscle. The augmented contractions in the hypertensive strain are due to an increased reactivity of the smooth muscle to oxygenderived free radicals. However, the lack of effect of the scavengers on endothelium-dependent contractions to acetylcholine suggests that the endothelium-derived contracting factor is chemically different from oxygen-derived free radicals.
KW - Cyclooxygenase
KW - Diltiazem
KW - Endothelium endothelium-derived contracting factor
KW - Thromboxane A
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U2 - 10.1161/01.HYP.13.6.859
DO - 10.1161/01.HYP.13.6.859
M3 - Article
C2 - 2567706
AN - SCOPUS:0024402398
SN - 0194-911X
VL - 13
SP - 859
EP - 864
JO - Hypertension
JF - Hypertension
IS - 6
ER -