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

Abstract

To investigate the effects of oestrogen supplementation after ovariectomy on systolic blood pressure and platelet aggregation on different sodium content diet in the female Dahl salt-sensitive rats. At 12 weeks of age, rats were ovariectomized or sham-operated and were fed either a high NaCl (8%) or low NaCl (0.3%) diet Ovariectomized rats were treated with either 17beta-oestradiol or placebo for 8 weeks, whereas sham-operated rats received placebo alone. After 8 weeks, the systolic blood pressure and platelet aggregation were measured and analysed by two-way analysis of variance. The systolic blood pressure of ovariectomized rats was significantly higher than that of sham-operated rats, and this increase in systolic blood pressure was suppressed by oestrogen supplementation. Systolic blood pressure was inversely correlated with plasma 17beta-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 diet, ovariectomy increased platelet aggregation, whereas hormone replacement did not improve it. In Dahl salt-sensitive rats fed a high sodium diet, hormone replacement reduced platelet aggregation. Oestrogen replacement suppresses the development of hypertension and attenuates platelet aggregatory function in the salt-loaded ovariectomized Dahl salt-sensitive rats. It has a potential to inhibit the atherosclerotic process in postmenopausal hypertension.