The inhibition of oxygen radical release from human neutrophil by resting platelets is reversed by administration of acetylsalicylic acid or clopidogrel

Resting platelets inhibit oxygen radical release from neutrophils. Antiplat elet therapy may support this function by preventing platelet activation Wh ether antiplatelet agents affect the antioxidative action of resting platel ets in the absence of platelet activation is unknown. The effect of acetyls alicylic acid or clopidogrel administration on the antioxidative action of resting platelets was therefore studied in ten healthy volunteers. Preparat ions of resting platelets were obtained from 5 subjects each - before, duri ng and after an eight-day course of daily treatment with 100mg of acetylsal icylic acid or 75mg of the thienopyridine clopidogrel. Human peripheral blo od neutrophils were pretreated with the platelets at a ratio of 1/50 for 45 min; then formyl-Met-Leu-Phe-triggered oxygen radical release was measured fluorometrically. The inhibitory effect of platelets on oxygen radical rel ease from neutrophils which was seen before treatment was abolished by anti platelet therapy with either of the drugs, and inhibition was restored grad ually after discontinuing acetlsalicylic acid/ clopidogrel intake. Results suggest that the protective role of resting platelets in controling oxygen radical release from neutrophils in the absence of platelet activation may he impaired by antiplatelet therapy.