Oxygen-free radicals and nitric oxide are involved in the thrombus growth produced by iontophoresis of ADP.

Thrombi have been induced by iontophoretic application of ADP on the venules of the mesentery of male Wistar rats (250-350 g). We determined the thrombus growth which is a reflection of platelet recruitment. We have demonstrated the ability of two oxygen-free radical scavengers, superoxide dismutase (SOD), a superoxide anion scavenger, and catalase, a hydrogen peroxide scavenger, to reduce thrombus growth. Imidazole, a thromboxane synthase inhibitor also reduces the thrombus growth. Dimethylthiourea, a hydroxyl radical scavenger, does not alter the thrombus size. The administration of a NO synthase inhibitor, Ng-nitro-L-arginine methyl ester (L-NAME), sharply increased the volume of the thrombus. Our results show the implication of superoxide anion, hydrogen peroxide and nitric oxide in platelet recruitment. (c) 1998 The Italian Pharmacological Society.