Effects of alpha-tocopherol on platelets and the coagulation system

Vitamin E is one of the most widely used antioxidants in cryopreservation and preservation technology. The objective of this study is to examine the effect of vitamin E on platelets and the coagulation system. Vitamin E was added at different concentrations in the range between 0.25 and 5 mM to donor plasma. Using a STA/STA Compact coagulation analyzer the following clotting tests were performed: prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT). The control clotting times PT (13.80 +/- 0.4 s), APTT (27.4 +/- 2.4 s) and TT (17.6 +/- 0.4 s) remained unchanged in the presence of vitamin E. The effect of vitamin E on platelets was assessed by platelet-induced clot retraction (PICR) and aggregation by thrombin. PICR was unaffected by vitamin E. Platelet aggregation, however, was profoundly inhibited by vitamin E. We found that inhibition of platelet aggregation by vitamin E was concentration dependent: increasing with increasing vitamin E concentration. This inhibitory effect, however, was widely reversible upon dilution of vitamin E with autologous platelet-poor plasma.