Relationship between Platelet Secretion and Prothrombin Cleavage in Native Whole Blood

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Abstract

To determine the relationship between platelet secretion and prothrombin conversion in whole blood, the release of platelet factor 4 and the generation of a Xa-specific cleavage product of prothrombin, fragment 1 + 2, were measured during the coagulation of whole blood. There was a parallel increase in the concentration of the two proteins. Over the first 5 min of incubation, platelet factor 4 concentration increased 6 ng/ml per min, and after 6-7 min, the rate of release increased to 750 ng/ml per min. Over the initial 5-7 min of incubation, fragment 1 + 2 concentration increased 1.5 pmol/ml per min with a subsequent increase of 45 pmol/ml per min. Incubation with 10 μM prostaglandin E1 or 15 μM prostaglandin I2 inhibited secretion of platelet factor 4 and delayed the onset of the rapid phase of fragment 1 + 2 generation by 8 min, while stimulation of platelet secretion with 1 μg/ml collagen suspension enhanced production of fragment 1 + 2. The addition of either 10 μM epinephrine or 100 ng/ml collagen suspension to whole blood did not affect either platelet factor 4 release or fragment 1 + 2 generation, although the combination of 3 μM epinephrine and 100 ng/ml collagen suspension enhanced platelet release and prothrombin cleavage.

Authors

Mary Ellen Rybak, Herbert K. Lau, Barbara Tomkins, Robert D. Rosenberg, Robert I. Handin