The endothelium‐dependent relaxation of rabbit aorta: effects of antioxidants and hydroxylated eicosatetraenoic acids

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Abstract
Acetylcholine (ACh) induced concentration‐dependent relaxations of rabbit aortic strips precontracted with noradrenaline. The relaxations were abolished if the endothelium of the strips was disrupted. Three different antioxidants (butylated hydroxytoluene, dithiothreitol and α‐tocopherol) reversed the endothelium‐dependent vasodilatation in a concentration‐dependent manner. However, the antioxidant ascorbic acid did not alter the vasodilatation. The hydroxylated eicosatetraenoic acids 5‐HETE, 12‐HETE, 15‐HETE and 5,12‐diHETE had no effect on aortic strips under basal or induced tension. These results suggest, that (non‐cyclo‐oxygenase) oxidation processes, insensitive to the action of ascorbic acid, represent a crucial step in the endothelium‐dependent dilatation of rabbit aorta by ACh. The hydroxylated fatty acids tested are unlikely to mediate this relaxation.