Direct electrochemical measurement of nitric oxide released from human platelets.

A porphyrinic microsensor has been used to investigate the release of nitric oxide (NO) from human platelets in whole blood and in washed platelet suspensions. Basal release of NO was not detectable. Aggregation of platelets by collagen (1-15 micrograms/ml) but not by thrombin (0.1 U/ml) resulted in a concentration-dependent release of NO. This release was prolonged and potentiated by L-arginine (100-1000 microM) and inhibited by NG-monomethyl-L-arginine (300 microM). These data support our previous findings that human platelets generate NO during aggregation.