The effect of acute or long-term genistein administration on the ischemia/reperfusion-induced arrhythmia in rats

Epidemiologic studies show that appearance of coronary artery disease in women rises after postmenopausal period.1,2 This situation is attributed to decreasing estrogen level in postmenopausal period.3 Phytoestrogen have been used to replace the estrogen in the post menopause period in women.4 Genistein is the most known phytoestrogen. It binds to estrogen receptor and act as like estrogen.5 In various studies, the cardio protective effect of genistein was shown.6,7 Phytoestrogen including genistein and others decreases symptom appearing in postmenopausal period; decreases the risk of heart attack, blood cholesterol, thrombocyte aggregation and increases angiogenesis and vasodilatation.8 It was indicated that genistein shows estrogenic effect in lower doses and antiestrogenic effect in higher doses.5 Genistein in lower doses decreases the ventricular arrhythmia and infarct sizes in ovariectomized female rats.1 Otherwise, it was also shown that genistein abolishes the antiarrhythmic effect of ischemic preconditioning in Langendorf perfused rats.9 Söylemez et al.10 observed that genistein alone was not found to be effective on the ischemia-induced arrhythmia. Long-term administration of genistein and its effects on the ischemia or reperfusion induced arrhythmia were not studied previously. However, in a study by Mendelsohn & Karas.2 It is reported that administration of genistein in lower doses for two days increased the contractility of myocardium and decreased contractility in higher doses (150uM). Moreover, there is only one study related with the acute effect of genistein on the reperfusioninduced arrhythmia.1 That is why it was aimed to research the effect of both long term and acute genistein administration on the ischemia and reperfusion induced arrhythmia in ovariectomized female and male rats in this study. Materials and methods