Dietary Estrogen Protects Against NaCl-Sensitive Hypertension in Estrogen-Depleted Female Spontaneously Hypertensive Rats.
In male spontaneously hypertensive rats (SHR) a high NaCl diet produces a rapid and sustained increase in hypertension. In contrast, in female SHR a high NaCl diet causes only a small, transient increase in arterial pressure. Elimination of most endogenous estrogen (via ovariectomy) produces mild NaCl-sensitive hypertension in female SHR, but simultaneous ovariectomy and elimination of exogenous dietary plant estrogens (phytoestrogens) nearly quadruples the hypertensive effect of the high NaCl diet, although phytoestrogen removal has a negligible effect on blood pressure in SHR fed a basal NaCl diet. This suggests that phytoestrogens (particularly genistein, the primary dietary phytoestrogen) protect ovariectomized female SHR from NaCl-sensitive hypertension. However, other reports suggest that the beneficial effects of phytoestrogens may only be present when genistein is combined with a high soy diet. The present study tests the hypothesis that genistein can independently reduce NaCl-sensitive hypertension in estrogen-depleted female SHR. Female SHR were ovariectomized at 3 weeks of age and placed on one of four casein-based, non-soy containing, diets (AIN-76A), i.e., a high (8%) or basal (0.6%) NaCl diet with or without genistein (0.06%; the approximate phytoestrogen concentration in the diet) added to the diet. After 5 weeks, femoral arterial catheters were implanted and 3 days later arterial pressures were recorded from all rats. The high NaCl diet increased arterial pressure by 68 ± 6 mm Hg in the phytoestrogen-free SHR, but produced only a 17 ± 5 mm Hg rise in arterial pressure in the genistein-supplemented group (similar to the rise previously observed in ovariectomized SHR fed a normal high NaCl diet). These results demonstrate that dietary genistein reduces NaCl-sensitive hypertension in ovariectomized female SHR. This work was supported by NHLBI Grant HL-37722.