Dietary administration of eicosapentaenoic and linolenic acid increases arterial blood pressure and suppresses vascular prostacyclin synthesis in the rat

The role of the ‘prostacyclin-thromboxane system’ in the regulation of arterial blood pressure was investigated in rats receiving diets which contained different amounts of eixosapentaenoic (EPA) and linolenic acid (LNA). Forty rats were divided into five groups of 8 animals, each group receiving 25 energy (en) % as fat. All diets contained equal amounts of linoleic acid (5 en%) and oleic acid (5 en%). In the control group I, the remaining 15 en% of fat were given as saturated fat. Two groups of animals received cod liver oil as a source for EPA in amounts of 2.5 (group II)_and 5 en% (group III) while the two remaining groups were given diets supplemented with linseed oil as a source for LNA in amounts of 2.5 (group IV) and 5 en% (group V), respectively. After six weeks of feeding period the animals were sacrificed and portions of their isolated aorta incubated in Tris buffer (pH 9.3) for determination of prostacyclin (PGI₂)-like activity. Arterial blood pressure was uncharged in group I animals, but significantly increased in all rats receiving dietary EPA or LNA supplements. This rise is arterial blood pressure was associated with a marked suppression of the appearance of PGI₂-like activity in the incubation buffer while platelet thromboxane release during blood clotting was unchanged. Our results show that dietary adminis- tration of EPA and LNA increases arterial blood pressure in the rat and that this effect is associated with a suppressed generation of vasodilator prostacyclin by vascular tissue.