The purpose of this study was to examine the effects of genistein on plasma lipid profiles and coronary vasodilation in ovariectomized rats at 4 and 10 weeks. The isolated arrested hearts were prepared to investigate coronary arteriolar responses to acetylcholine (Ach;10[superscript -5] M) and sodium nitroprusside (SNP; 10[superscript -4] M). Changes in diameter to topical applications of these agents were determined by using intravital fluorescence microscopy and digital image processing analysis. The results assessed by means percent changes of studied arteriolar diameter indicated that the impairment of coronary arterioles to Ach were significantly obtained in ovariectomized rat as compared to their age-matched controls. Interestingly, these abnormalities of arteriolar responses were attenuated by daily injection of genistein (0.2 mg/kg bw/day). However, in the experiments using SNP found that there was no significant difference among those groupsof sham ovariectomized rats, ovariectomized rats and ovariectomized injection with genistein. Moreover, bilateral ovariectomy and treatment with genistein did not alter the lipid profiles and the cardiovascular functions includings systolic blood pressure, diastolic blood pressure, mean arterial blood pressure and heart rate. It may conclude that genistein could prevent endothelial dysfunction in ovariectomized rats
