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 ovariectomy on systolic blood pressure and platelet aggregation on different sodium content diet in the female Dahl salt-sensitive rats.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Department of Internal Medicine, School of Medicine, Keio University, Tokyo.
T
T
Sasaki
Y
Y
Ohno
K
K
Otsuka
T
T
Suzawa
H
H
Suzuki
T
T
Saruta
D000284:Administration, Oral; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004958:Estradiol / Q000008:administration & dosage*; D005260:Female; D020249:Hormone Replacement Therapy; D006973:Hypertension / Q000097:blood / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010052:Ovariectomy; D010974:Platelet Aggregation / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D020303:Rats, Inbred Dahl; D012982:Sodium, Dietary / Q000633:toxicity*
D012982:Sodium, Dietary; D004958:Estradiol; D019331:NG-Nitroarginine Methyl Ester