Key result
Platelets stimulated by ionophore A23187 or collagen plus thrombin exhibited shorter clotting times than could be explained by minor cell lysis or factor V release alone.
The study confirms that strong platelet agonists like ionophore A23187 or collagen plus thrombin induce significant procoagulant activity beyond what is explained by cell lysis or factor V release.
Challenges prior attribution of procoagulant activity to intact platelet activation; leaves open in vivo mechanisms and clinical relevance.
The procoagulant activity of activated platelets in a one-stage prothrombinase assay is reevaluated. It is shown that the apparent procoagulant activity of platelets activated by ADP or collagen can be explained by minor cell lysis accompanying platelet activation. The reduction in clotting time observed with thrombin activated platelets can be explained by a combined effect of minor cell lysis and release and activation of factor V from the platelets. Platelets stimulated by ionophore A23187 or by the combined action of collagen plus thrombin show a much shorter clotting time than can be accounted for by minor platelet lysis or release and activation of factor V from the platelets. The results with this clotting assay essentially confirm previous observations [Bevers et al.: Eur. J. Biochem. 122:429-436, 1982] using a spectrophotometric method with highly purified coagulation factors and a chromogenic substrate to measure the rate of thrombin formation with activated platelets.
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Bevers et al. (2009) studied Platelet procoagulant activity. Platelet stimulation (ADP, collagen, thrombin, ionophore A23187) was evaluated on Clotting time in a one-stage prothrombinase assay. Platelets stimulated by ionophore A23187 or collagen plus thrombin exhibited shorter clotting times than could be explained by minor cell lysis or factor V release alone.
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