Effect of estrogen on myocardial ischemia-reperfusion injury in male and female rats and related mechanism

Abstract

Due to the difference of estrogen levels in different phases of estrous cycle, it is necessary to exclude the influence of endogenous estrogen when studying the cardiovascular effects of estrogen and its analogues. In this study, the ischemia/reperfusion (I/R) injury of isolated heart were investigated in female rats during different phases of estrous cycle with male rats as comparison. The results indicated that the estrogen content in blood of rats during metestrus and diestrus (MD) was lower than those during proestrus and estrous (PE). 17β-Estradiol (E2) at 10^-8 M did not show significant effects on I/R injury in male rats and female rats during PE. However, E2 exerted an obviously protective effects against I/R injury on heart rate (HR), lactate dehydrogenase (LDH) and creatine kinase (CK) release in female rats during MD. Furthermore, E2 relieved I/R injury in female rats during MD by decreasing the infarct size and the expression level of p-CaMKII. The results suggested estrous cycles may influence on the extent of cardiac I/R injury due to the regulation of E2 on CaMKII expression level, providing an idea that the estrus cycle should be considered for animal model preparation and toxicity studies in estrogen and environmental hormone research.

Keywords: CaMKII; Cardioprotection; Estrogen; Estrous cycle; Myocardial ischemia–reperfusion.