Captopril Administration Reduces Thrombus Formation and Surface Expression of Platelet Glycoprotein IIb/IIIa in Early Postmyocardial Infarction Stage

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Abstract
Abstract —Long-term administration of the angiotensin-converting enzyme inhibitor captopril in survivors of myocardial infarction (MI) reduces the risk of cardiovascular death, recurrence of MI, and unstable angina, suggesting that captopril may posses antithrombotic properties that have not been clearly elucidated. We assessed the short-term antithrombotic effects of captopril on platelet aggregation, platelet-subendothelium interaction, and the expression of major glycoproteins on platelet surface. A double-blind study was carried out in 25 patients with MI. Blood samples were taken before (baseline) and 12 days after treatment in both the control and captopril groups. Platelet aggregation was tested by conventional aggregometry using common activating agents. Platelet interaction with deeply damaged subendothelial surface was evaluated in a perfusion model, with blood maintained under flow conditions. Deposition of platelets was quantified by using computer-assisted morphometric techniques on histological sections, and it was expressed as a percentage of total vessel surface covered by platelets (CS) and as a ratio between large aggregates (T) and surface covered by platelets (100×T/CS). Glycoprotein expression was measured using flow cytometric techniques. Aggregometric responses showed no significant variations; however, in the captopril group, 100×T/CS decreased after 12 days of treatment (100×T/CS: 36±12.1% captopril versus 64±8.0% baseline; P =0.05). This parameter was also significantly decreased from that found in control group patients (100×T/CS: 67±4.5%; P =0.008). Flow cytometry showed a 30% reduction in glycoprotein IIb/IIIa expression ( P =0.02). Captopril reduced the formation of large aggregates in a perfusion system, which might be related to a down-regulation of glycoprotein IIb/IIIa complex on the platelet surface. These results suggest that captopril exerts an antiplatelet effect that may contribute to its beneficial action in MI.

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