Rabbit aorta predominantly synthesizes prostacyclin (PGI2), a potent inhibitor of platelet aggregation and a strong vasodilator. We report here the effect of vitamin E depletion and repletion on endogenous release of PGI2 by rabbit aorta. Serum pyruvate kinase was monitored for myopathy. The endogenous release of PGI2 by the aorta, detected as its stable metabolite 6-keto-PGF1 alpha, was inhibited by indomethacin and was inversely related to the size of aorta sections. Deficient aorta synthesized significantly less PGI2 than those from control animals. Repletion of deficient animals for 48 h completely restored the PGI2 release to a level comparable to the control values. The data showed that PGI2 synthesis by aorta can be influenced by dietary vitamin E.