Estrogen receptor antagonism exacerbates cardiac structural and functional remodeling in female rats

We have previously demonstrated the cardioprotective effects of ovarian hormones against adverse ventricular remodeling imposed by chronic volume overload. Here, we assess the estrogen receptor dependence of this cardioprotection. Four groups of female rats were studied: sham-operated (Sham), volume overloaded [aortocaval fistula (ACF)], Sham treated with estrogen receptor antagonist ICI 182,780 (Sham + ICI), and ACF treated with ICI. Cardiac function was assessed temporally using echocardiogram, and tissue samples were collected at 5 days and 6 wk postsurgery. All rats with volume overload had significantly increased cardiac output (96 ± 32 ml/min for ACF and 108 ± 11 ml/min for ACF + ICI vs. 31 ± 2 for Sham, P < 0.05). At 6 wk, volume overload induced significant left ventricular (LV) hypertrophy in both untreated and treated ACF groups. Both ACF groups developed significantly increased LV end-diastolic diameter (LVEDD), indicating LV dilatation, with the ACF + ICI group having the greatest increase (340%, relative to Sham). Ejection fraction was significantly reduced in the ACF + ICI group (23% reduction) at 6 wk postsurgery compared with untreated ACF (P < 0.05). Interstitial collagen staining was significantly reduced by volume overload, with estrogen receptor antagonism causing greater collagen loss at both 5 days and 6 wk postsurgery. Furthermore, volume overload induced a significant increase in LV wall stress only in rats treated with estrogen antagonist. These data indicate that estrogen receptor signaling is essential for sex hormone-dependent cardioprotection against adverse remodeling. The maintenance of myocardial extracellular matrix collagen appears to play a key role in this cardioprotection. NEW & NOTEWORTHY: We assessed the estrogen receptor (ER) dependence of female-specific cardioprotection using a rat model of chronic volume-overload stress. ER antagonism worsened ventricular wall stress, ventricular dilation, and cardiac dysfunction induced by volume overload. Further, blocking ERs resulted in cardiac remodeling and functional changes similar to that previously found in ovariectomized rats.