Oestrogen attenuates the increases in blood pressure and platelet aggregation in ovariectomized and salt-loaded Dahl salt-sensitive rats

Objective To investigate the effects of oestrogen supplementation after ova riectomy on systolic blood pressure and platelet aggregation on different s odium content diet in the female Dahl salt-sensitive rats. Methods At 12 weeks of age, rats were ovariectomized or sham-operated and w ere fed either a high NaCl (8%) or low NaCl (0.3%) diet Ovariectomized rats were treated with either 17 beta-oestradiol or placebo for 8 weeks, wherea s sham-operated rats received placebo alone. After 8 weeks, the systolic bl ood pressure and platelet aggregation were measured and analysed by two-way analysis of variance. Results The systolic blood pressure of ovariectomized rats was significantl y higher than that of sham-operated rats, and this increase in systolic bro od pressure was suppressed by oestrogen supplementation. Systolic blood pre ssure was inversely correlated with plasma 17 beta-oestradiol levels (r = - 0.77, P < 0.01) and with the uterus weight to body weight ratio (r = -0.47, P < 0.01). Platelet aggregation was significantly enhanced by salt loading . Salt loading and female hormonal manipulation significantly interacted on platelet aggregation. Only in Dahl salt-sensitive rats fed a low sodium di et, ovariectomy increased platelet aggregation, whereas hormone replacement did not improve it. In Dahl salt-sensitive rats fed a high sodium diet, ho rmone replacement reduced platelet aggregation. Conclusions Oestrogen replacement suppresses the development of hypertensio n and attenuates platelet aggregatory function in the salt-loaded ovariecto mized Dahl salt-sensitive rats. It has a potential to inhibit the atheroscl erotic process in postmenopausal hypertension. J Hypertens 2000, 18:911-917 (C) Lippincott Williams & Wilkins.