Thrombolytic therapy is known to induce platelet-related side effects. We used a parallel-plate flow chamber, which was connected to the femoral artery of the rat, to measure platelet adhesion ex vivo. A collagen-coated arterioarterial shunt between two carotid arteries was used to measure shunt patency duration as an index of antithrombotic efficacy. Tissue-type plasminogen activator (t-PA), vitamin E, and the combination of these two were intravenously administered for 60 min. Measurements were performed before drug administration, and at 30, 60, 120 min after the initiation of drug infusion. Our results indicated that (1) treatments with t-PA or t-PA/vitamin E prolonged the time to shunt occlusion at 30 and 60 min; (2) t-PA enhanced platelet adhesion at 60 and 120 min; (3) vitamin E tended to reduce platelet adhesion; (4) t-PA/vitamin E reduced the t-PA-enhanced platelet adhesion; (5) at the high-density area of platelet adhesion under t-PA treatment, the adherent platelets demonstrated severe morphological changes which could be blocked by vitamin E. These data suggest that t-PA may enhance platelet adhesion in rats and that this adverse effect can be suppressed by co-administration of vitamin E.
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