The endothelium-dependent relaxation of human middle cerebral artery: effects of activated neutrophils.

Neutrophils, activated by 4 beta-phorbol-12 beta-myristate-13 alpha-acetate, decreased acetylcholine-induced relaxation of strips of human middle cerebral artery precontracted with noradrenaline. This effect was prevented by catalase, but not by superoxide dismutase. Nifedipine, propranolol and, less markedly, captopril reduced the decrease in acetylcholine-induced relaxation. Aspirin and dipyridamole did not reduce it.