Effects of dietary phytoestrogen on global myocardial ischemia-reperfusioninjury in isolated female rat hearts

We investigated the effects of phytoestrogen on global myocardial ischemia- reperfusion injury in five groups of female rats. A high-phytoestrogen grou p (HPE) was ovariectomized (Ovx) and fed a diet containing soybean protein and a high-isoflavone soy extract. Another Ovx group of rats was fed the sa me diet as the HPE group but treated with the estrogen receptor blocker ICI -182,780 (HPE + ICI). A third group of Ovx rats was fed a diet containing s oybean protein alone (low-phytoestrogen content; LPE). A fourth Ovx group w as fed a diet free of phytoestrogen (Ovx). The fifth group of rats was sham ovariectomized (sham). Hearts from all rats were subjected to 30 min of gl obal, hypothermic (4 degreesC), cardioplegic ischemia and 120 min of normot hermic (37 degreesC) reperfusion with oxygenated Krebs-Henseleit buffer. Co mpared with either the sham or the HPE group, the Ovx and HPE + ICI groups had significantly decreased first derivative of left ventricular pressure ( dP/dt), coronary flow rate (CFR), nitrite production and mitochondrial resp iratory function and significantly increased Ca2+ accumulation and myocardi al histological and ultrastructural injury. The CFR of the LPE group was si gnificantly different from that of either Ovx or HPE + ICI group but the dP /dt, nitrite production, Ca2+ accumulation, and mitochondrial function were not. Our results indicate that diets containing phytoestrogen extract play a cardioprotective role in global myocardial ischemia-reperfusion in femal e rats.