Bradykinin induces superoxide anion release from human endothelial cells

The time‐dependent release of superoxide anion (O  2− ) from bradykinin (Bk)‐stimulated human umbilical vein endothelial cells (EC) was measured as the superoxide dismutase‐inhibitable reduction of ferricytochrome C employing a novel application of microspectrophotometry. In the absence of Bk, O  2− release by EC was not detectable. EC exposure to Bk (10−6 to 10−5 M) resulted in a rapid release of O  2− . The release of O  2− occurred within 5 minutes of exposure. O  2− release was partially inhibited by indomethacin (63 ± 6%), thus suggesting that arachidonic acid metabolism, through cyclooxygenase, contributes to EC O  2− production. EC O  2− release may be an important component in the pathophysiologic actions of Bk on vascular function.