Effects of oestrogen replacement on steady and pulsatile haemodynamics in ovariectomized rats

Abstract

1 The effects of ovariectomy (Ovx), menopause and oestrogen replacement on the haemodynamics remain controversial. The present study employed the technique of arterial impedance analysis to measure and calculate the steady and pulsatile haemodynamics. The purpose was to determine the haemodynamic consequence of ovariectomy and oestrogen replacement. 2 Ovariectomy was carried out under anaesthesia on female Sprague Dawley rats aged 9 weeks. Oestrogen (17 β-estradiol or E2) replacement started 1 week after ovariectomy for 4 weeks. Ovx increased the body weight (BW), while it greatly reduced the uterus weight. Left ventricular weight (LVW) was slightly increased, but LVW/BW ratio was slightly reduced. These changes were reversed after E2 replacement. 3 Compared to sham group, Ovx with or without E2 replacement did not significantly affect the systolic, mean and diastolic pressure. In Ovx, pulse pressure (PP) and heart rate were significantly increased, while stroke volume and cardiac output were slightly decreased. Total peripheral resistance (TPR) was largely elevated, indicating Ovx induced systemic vasoconstriction. These changes all returned to close normal values (sham group) after E2 replacement, except PP. 4 Ovx increased the characteristic input impedance (Zc) and pulse wave reflection, while it decreased arterial compliance. E2 treatment reversed these changes, except Zc. 5 These results demonstrate that Ovx influences both the resistance and Windkessel functions of the artery. E2 treatment effectively reverses most the effects of Ovx both on the steady and pulsatile haemodynamics.