N-3 fatty acids reduce in vitro thromboxane production while having little effect on in vitro prostacyclin production in the rat

Abstract

Male Sprague-Dawley rats were fed diets with 50% of the energy from fat over a 20-day period. The fats used were hydrogenated beef-fat (HBF), or HBF supplemented with ethyl arachidonate A, safflower oil (SO), or a mixture of SO and linseed oil (LO). For comparative purposes, another group of animals was fed a diet providing 50% of the energy as butter-fat. In vitro aortic prostacyclin (PGI 2) and serum thromboxane (TXA 2) levels (from clotting blood) were determined by radioimmunoassay of 6-keto PGF 1α and TXB 2, respectively. The HBF diet had similar AA levels relative to the butter-fed rats but significantly reduced tissue levels of eicosapentaenoic acid (EPA) and this was associated with an increased production of serum TXB 2. Supplementing the HBF diet with AA increased tissue levels of AA while maintaining low levels of n-3 fatty acids. These changes were accompanied by significant increases of both TXB 2 and 6-keto-PGF 1α. LO supplementation to the HBF diet (with constant SO) led to elevated levels of EPA and relatively constant AA levels and this was associated with reduced producton of TXB 2. These results highlight the responsiveness of TXA 2 to n-3 fatty acids in contrast to PGI 2 which was more influenced by the level of AA in the tissue phospholipids in the rat.