Differential Effects of Megavitamin E on Prostacyclin and Thromboxane Synthesis in Streptozotocin-Induced Diabetic Rats

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Abstract
Diabetic subjects tend to develop microvascular complications believed to be due to platelet hyperaggregability. This increased platelet sensitivity is thought to be the result of an imbalance of PGI2 and TXA2 production in diabetes. This study sought to determine whether megavitamin E supplementation could restore PGI2/TXA2 balance in streptozotocin-diabetic rats. Endogenous release of PGI2 by isolated aorta, determined via radioimmunoassay of its stable metabolite, 6-keto-PGF1, α, was significantly greater (P< 0.05) in rats receiving 100x the normal vitamin E requirement than in untreated diabetic rats. PGI2 synthesis was negatively correlated with plasma glucose levels (r = -0.87, P< 0.05) in non-fasted rats at sacrifice. Vitamin E supplementation, at both the 10x and the 100x level, significantly depressed (P< 0.05) thrombin-stimulated synthesis of TXA2 in washed platelet. PGI2 and TXA2 production were expressed as a ratio. Megavitamin E therapy appears to increase this ratio over that seen in the diabetic animal. The data suggest that vitamin E, at high levels, exerts an ameliorating influence of the PGI2/TXA2 imbalance of diabetes.

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