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Differential Effects of Dietary Vitamin E and Antioxidants on Eicosanoid Synthesis in Young Rabbits¹

Alvin C. Chan^*,2, E. Thackeray Pritchard and Patrick C. Choy

^* Department of Foods and Nutrition, Department of Oral Biology Department of Biochemistry, University of Manitoba, Winnipeg, Manitoba R3E 0W3 Canada

This study was designed to evaluate the effects of dietary vitamin E and synthetic antioxidants on prostacyclin (PGI₂) synthesis in isolated aorta segments and perfused hearts as well as thromboxane (TxA₂) synthesis in thrombin-stimulated washed platelets. Weanling male New Zealand rabbits were fed a vitamin E-deficient basal diet or the basal diet supplemented with either all-rac--tocopherol acetate or propyl gallate or DPPD (N,N'-diphenyl-p-phenylenediamine). After 30 days on the diet, plasma tocopherol level, pyruvate kinase and liver microsomal NADPH oxidase were determined. DPPD but not propyl gallate prevented the development of myopathy. None of the synthetic antioxidants could substitute for vitamin E in decreasing enzymatic lipid peroxidation. PGI₂ release by the aorta was lowered in vitamin E deficiency and was highest with DPPD supplementation. In the Langendorff perfused heart, however, PGI₂ release was highest in the vitamin E-deficient group, possibly due to cardiomyopathy. TxA₂ synthesis by washed platelets challenged with thrombin was independent of the antioxidant status of the animal. The data showed that dietary antioxidants selectively affect eicosanoid synthesis in different tissues.

KEY WORDS: • vitamin E • antioxidants • prostacyclin (PGI₂) • thromboxane (TxB₂) • aorta • perfused heart • platelet • rabbit

¹ Supported in part by grants from the Canadian Medical Research Council and Natural Sciences and Engineering Research Council Canada. A preliminary report of this work was presented at FASEB meeting, April, 1982 in New Orleans, LA. Fed. Proc. 41, 344 (1982).

² Present address: Assistant Professor, Department of Biochemistry, University of Ottawa, Ottawa, Ontario KIN 9B4 Canada.

Manuscript received 27 September 1982.