Effects of methionine on endogenous antioxidants in the heart

The deficiency of methionine, an essential amino acid, is associated with c ardiovascular lesions. Because different types of cardiac pathologies are c aused by a decrease in antioxidants, we examined the effects of methionine on myocardial antioxidant enzymes in hemodynamically assessed rats that wer e treated with methionine (10 mg/ml) in drinking water for 12, 24, and 48 h . Glutathione peroxidase (GSHPx) activity was significantly increased to 15 0.5 +/- 12.2 and 191.7 +/- 13.7% of the control value at 12 and 24 h, respe ctively, followed by a decline to 120 +/- 24.6% at 48 h. The mRNA levels of GSHPx at these time points were 151.2 +/- 12.0, 218.7 +/- 35.3, and 173.5 +/- 25.2%, respectively. Superoxide dismutase (SOD) activity was 144.3 +/- 3.7, 114.3 +/- 10.1, and 143.1 +/- 11.2% at 12, 24, and 48 h, respectively. Catalase (Cat) activity was 272.4 +/- 5.4, 237.8 +/- 16.6, and 224.1 +/- 1 7.3% of the control value. The expression of Cat and SOD mRNA was unchanged at 12, 24, and 48 h. The lipid peroxidation was decreased by 24.4 +/- 11.2 , 54.9 +/- 0.1, and 6.4 +/- 2.1% at 12, 24, and 48 h, respectively. Methion ine had no effect on the ventricular or aortic pressures, heart rate, and m yocardial glutathione levels at any of the time points. The study shows tha t methionine has a significant effect on the myocardial antioxidant enzyme activities, and only changes in GSHPx enzyme activity correlated with the m RNA changes. These antioxidant changes may have a role in the beneficial ef fects of methionine in pathological rather than physiological conditions.