Preincubating platelet-rich plasma (PRP) of
vitamin E-deficient rats with RRR-
alpha-tocopherol prior to the aggregation induced by
collagen suspension resulted in inhibition of the formation of endoperoxide metabolites derived from endogenous
arachidonic acid (AA). This inhibition was not dose dependent at concentrations above the plasma level of RRR-
alpha-tocopherol of
vitamin E-supplemented rats. Preincubating the
vitamin E-deficient PRP with RRR-
alpha-tocopherol did not affect the formation of 12-hydroxyeicosatetraenoic
acid, the platelet
lipoxygenase product. Concentrations of endoperoxide metabolites in diluted whole blood challenged with
collagen suspension were significantly greater in the
vitamin E-deficient group than the supplemented group. The level of AA in platelet or plasma
phospholipids was not different between the two groups. However, blood platelet counts in the deficient group were significantly greater than those of the supplemented group. Concentrations of endoperoxide metabolites in PRP samples in which platelet concentrations were equalized were still greater in
vitamin E-deficient group; however, the difference was not statistically significant. There was also no difference in the degree of maximal platelet aggregation between the two groups. These results indicated that
vitamin E deficiency can slightly stimulate the formation of
cyclooxygenase products derived from endogenous AA, but it did not affect the formation of
lipoxygenase product in rat platelets.