beta2-Adrenoceptor confers cardioprotection against hypoxia in isolated ventricular myocytes and the effects depend...

Estrogen plays a cardioprotective role in female rat hearts subjected to ischemia/reperfusion injury. The its effects are, at least partially, associated with decreased cardiomyocyte contraction and increased expression of beta(2)-adrenoceptor (beta(2)-AR). We tested whether beta(2)-AR could be involved in cardioprotection against ischemic damage and whether the roles of beta(2)-AR were dependent on estrogenic environment. We first determined the effects of hypoxia/reoxygenation (H/R) on cardiomyocyte shortening in female rats. We then determined the roles of beta(2)-AR in cardiomyocyte shortening, lactate dehydrogenase (LDH) release in culture medium, and cell death during hypoxia in isolated myocytes from female rats. We further determined the effects of estrogen on the roles of beta(2)-AR during hypoxia. H/R induced short-term hibernation and stunning at the level of ventricular myocytes from normal female rats. Inhibition of beta(2)-AR with ICI118,551 significantly elevated adrenergic contractile reserve, myocardial injury, and cell death in normal female rats during hypoxia, whereas ovariectomy (OVX) prominently enhanced myocyte contraction, myocardial injury, and cell death, and deprived the alternations in normal female rats. These changes were restored to normal by estrogen replacement (OVX+E(2)). These data suggest that beta(2)-AR may be involved in the cardioprotection against ischemic damage, and the cardioprotection may depend on estrogenic environment.