Summary
The role of superoxide anions (O2
−) in human platelet aggregation in Krebs’ buffer or plasma was investigated. In indome thacin (10 μM)-treated washed platelets superoxide dismutase (SOD; 60 U/ml) or ferricytochrome c (FCC; 70 μM) inhibited platelet aggregation by thrombin but not that by collagen or ADP. In addition, in indomethacin (10 μM)-treated washed platelets, SOD significantly potentiated the anti-aggregatory activity of prostacyclin (PGI2) or iloprost when thrombin but not collagen was used as the aggregating agent. In platelet rich plasma, SOD (60 U/ml) did not inhibit platelet aggregation nor did it potentiate the anti-aggregatory activity of iloprost when ADP, collagen or thrombin were used as aggregating agents. Thus, O2
− participate in the aggregatory activity of thrombin but not collagen or ADP and PGI2 or iloprost, by reducing the sensitivity of platelets to thrombin, co-operate with SOD to inhibit thrombin-induced platelet aggregation
The interpretation of the use of SOD in experiments involving endothelium-derived relaxing factor (NO) is discussed
