EFFECTS OF ALPHA-TOCOPHEROL (VITAMIN-E) ON THE ULTRASTRUCTURE OF HUMAN PLATELETS INVITRO

Washed human platelets were incubated with increasing concentrations o f alpha-tocopherol. Spontaneous aggregation was induced by tocopherol (0.5 mM or above). Aggregation was inhibited by ethylenediaminetetraac etate and platelet activation was reduced by prostaglandin E1. Using e lectron microscopy, it was confirmed that tocopherol caused platelet d isruption to some extent and the released components may have generate d aggregation. These effects were not observed in platelet-rich plasma . Spontaneous activation was not observed when the concentration of to copherol was 0.03 mM or lower. Concentrations of tocopherol between 0. 075 mM and 0.0075 mM had inhibiting influences on activation of washed platelets by thrombin. Tocopherol (between 0.1 mM and 0.005 mM) chang ed activation of washed platelets by cationized ferritin in that it fa cilitated the first phase of aggregation but reduced the second phase in an indirect proportional manner. The results show that the effects of tocopherol in washed platelet preparations are not comparable to th ose observed in plasma and that the platelet membrane must be regarded as a crucial target for vitamin E.