Docosahexaenoic acid, but not eicosapentaenoic acid, lowers ambulatory blood pressure and shortens interval QT in spontaneously hypertensive rats in vivo

This study was designed to evaluate the effects of individual dietary long-chain n-3 polyunsaturated fatty acids (LCPUFA) on hypertension and cardiac consecutive disorders in spontaneously hypertensive rats (SHR) as compared to Wistar-Kyoto rats (WKY). Rats were fed for 2 months an eicosapentaenoic (EPA)- or docosahexaenoic acid (DHA)-rich diet (240 mg/day) or an n-3 PUFA-free diet. Male SHR (n=6), implanted with cardiovascular telemetry devices, were housed in individual cages for continuous measurements of cardiovascular parameters (blood pressure (BP) and heart rate (HR)) during either activity or rest periods, ECG were recorded during the quiet period. The n-6 PUFA upstream of arachidonic acid was affected in SHR tissues. The cardiac phospholipid fatty acid profile was significantly affected by dietary DHA supply, and EPA in a very lower extent, since DHA only was incorporated in the membranes instead of n-6 PUFAs. Endothelium n-6 PUFA content increased in all SHR groups. Compared to WKY, linoleic acid content decreased in both studied tissues. Cardiac noradrenalin decreased while the adrenal catecholamine stores decreased in SHR as compared to WKY. Both n-3 PUFA supply induced a decrease of adrenal catecholamine stores. Nevertheless after 6 weeks, DHA but not EPA induced a lowering-blood pressure effect and shortened the QT interval in SHR, most probably through its tissue enrichment and a specific effect on adrenergic function. Dietary DHA supply retards blood pressure development and has cardioprotective effect. These findings, showing the cardioprotective effects of DHA in living animals, were obtained in SHR, but may relate to essential hypertension in humans.