Oestrogen changed cardiomyocyte contraction and β‐adrenoceptor expression in rat hearts subjected to ischaemia–reperfusion

Abstract

Women with functional ovaries have a lower cardiovascular risk than men and postmenopausal women. However, oestrogen replacement therapy remains controversial. This study examined the effect of ovarian hormone deficiency and oestrogen replacement on ventricular myocyte contractile function and expression of beta-adrenoceptors (beta-ARs). Female Sprague-Dawley rats were subjected to bilateral ovariectomy (OVX) or sham operation (Sham). A subgroup of OVX rats received oestrogen (E2) replacement (40 microg kg(-1) day(-1)) for 4 weeks. Cardiomyocyte shortening was evaluated in basal conditions and in the presence of isoprenaline (ISO). The expression of beta-ARs was assessed by Western blotting. The presence of lactate dehydrogenase (LDH) activity in the coronary effluent was determined. Ovariectomy promoted body weight gain associated with reduced serum E2 and uterine weight, all of which were abolished by treatment with E2. Ovariectomy increased the amplitude of both basal and ISO-stimulated contractions, increased LDH release, upregulated beta1-AR expression and downregulated beta2-AR expression, all of which were restored by treatment with E2. A beta1-AR antagonist, CGP20712A, but not a beta2-AR antagonist, ICI118,551, significantly decreased the amplitude of ventricular myocyte shortening. Oestrogen decreased cardiomyocyte contraction and the expression of beta1-AR, and increased expression of beta2-AR, and all these effects were abolished by the E2 receptor antagonist, ICI182,780. These data suggest that oestrogen plays a cardioprotective role in female rat hearts subjected to ischaemia-reperfusion injury, and the effects of oestrogen are associated with decreased cardiomyocyte contraction and expression of beta1-AR, and increased expression of beta2-AR.