Acute myocardial infarction (MI) is the leading cause of mortality worldwide with premenopausal women showing a lower incidence of cardiovascular disease compared with men of the same age. After menopause, this advantage disappears, suggesting that sex hormones play a cardioprotective role. This study was aimed to assess on the activity of antioxidant enzymes in plasma and the respiratory function of isolated heart mitochondria after the induction of MI in rats after ovariectomy and estradiol benzoate supplementation. Sprague-Dawley female rats were ovariectomized 3 months before the induction of MI and supplemented/not supplemented with oestrogen 3 months before/7 days after the induction of MI. No significant differences in glutathione peroxidase activities were found in any group. Differences between values were only significant in the ovariectomized not supplemented group (P < 0.01) for the glutathione reductase activity and glutathione concentrations. In isolated mitochondria (7 days after MI), the decline in respiration was observed comparing the ovariectomized and nonovariectomized group. Respiratory functions did not show significant differences between animals supplemented with oestrogen before MI or treated with oestrogen after MI. Ovariectomy worsened mitochondrial dysfunction after MI, and oestrogen supplementation before or after the induction of MI did not improve mitochondrial function.
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