Estrogen depletion induces NaCl-sensitive hypertension in female spontaneously hypertensive rats

In women, arterial pressure generally increases after menopause, but severa l studies suggest that women who eat large amounts of plant estrogens (phyt oestrogens) experience a slower rise in the incidence of postmenopausal hyp ertension. This suggests that both ovarian hormones (principally estrogen) and phytoestrogens may protect at least some women from hypertension. The p resent study tests the hypothesis that phytoestrogens blunt hypertension in estrogen-depleted female spontaneously hypertensive rats (SHR). Three-week -old ovariectomized SHR were fed one of four diets that contained basal (0. 6%) or high (8%) NaCl with or without dietary phytoestrogens for 9 wk. In S HR on the basal NaCl diet, arterial pressure was unaffected by the removal of dietary phytoestrogens. In contrast, in SHR on the high-NaCl diet, arter ial pressure was significantly higher in rats on the phytoestrogen-free (20 4 +/- 4 mmHg) compared with the phytoestrogen-replete (153 +/- 4 mmHg) diet . Ganglionic blockade resulted in reductions in arterial pressure that were directly related to the dietary NaCl-induced increases in arterial pressur e. Together, these data indicate that dietary phytoestrogens protect ovarie ctomized female SHR from dietary NaCl-sensitive hypertension and that the s ympathetic nervous system plays an important role in this effect. Furthermo re, these results demonstrate that dietary phytoestrogens can have a major impact on the interpretation of studies into the physiological role of estr ogen in females.