Docosahexaenoic acid is an antihypertensive nutrient that affects aldosterone production in SHR

The effects of dietary docosahexaenoic acid (DHA), an omega-3 polyunsaturat ed fatty acid, on blood pressure and some pressure-regulating systems were measured in young spontaneously hypertensive rats (SHR). Plasma aldosterone end corticosterone levels, adrenal aldosterone production in vitro,and cha racteristics of adrenal angiotensin receptors were measured after 6 weeks o f diet. Renal cytochrome P450 (CYP) 4A gene expression and arachidonic acid metabolism by renal microsomes were also investigated. Plasma cholesterol, triglycerides, and high-density lipoprotein cholesterol were measured. Die ts contained either corn/soybean oil alone (CSO), or oil enriched with DHA. After 6 weeks, rats fed DHA had systolic blood pressures averaging 34 mmHg less than controls (P < 0.001). Plasma aldosterone levels were 33% lower i n the DHA-fed animals than in controls (22 +/- 3 vs. 33 +/- 3.7 ng/dl, P < 0.05). Plasma levels of corticosterone were 18% lower in animals fed DHA th an In controls, but this difference was not statistically significant. Adre nal glomerulosa cells from DHA-fed rats produced less aldosterone in vitro in response to angiotensin II, ACTH, or potassium. The difference was less marked when aldosterone production was stimulated by supplying exogenous co rticosterone, suggesting an effect of DHA on postreceptor steps in signal t ransduction or the early pathway of aldosteronogenesis. We found no signifi cant differences in angiotensin receptor subtype, number, or affinity. Prod uction of arachidonic epoxides by renal microsomes was 17% lower in DHA-fed animals than in controls (P < 0.05), Renal cortical mRNA levels of CYP4A g enes and formation of 19- and 20-hydroxyeicosatetraenoic acid (HETE) did no t differ between dietary groups. Plasma total cholesterol and high-density- lipoprotein (HDL) levels were significantly reduced in SHR fed the DHA supp lement, but triglyceride levels were not significantly different The effect s of DHA on steroid and eicosanoid metabolism may be part of the mechanism by which this fatty acid prevents some of the hypertension in growing SHR.